A study of HIV seroprevalence in a group of homeless youth in Hollywood, California.

The objective of this descriptive-exploratory study was to examine the HIV seroprevalence rate among a sample of homeless youth in Hollywood, California. A total of 96 respondents (age 14-24) were administered a questionnaire and had their blood drawn to test for the presence of HIV antibodies, during nightly street outreach activities conducted by Covenant House California. The HIV seroprevalence rate was 11.5% for the sample. Chi-square analysis showed strong correlation between HIV status and sexual risk behavior but not for HIV status and drug-related risk behavior.

Transforming growth factor-alpha expression in peritoneal macrophages elicited from SENCAR and B6C3F1 mice: responses to lipopolysaccharide and 12-O-tetradecanoylphorbol-13-acetate.

Recent findings in our laboratory indicated that peritoneal macrophages (MPs) elicited from phorbol ester-sensitive SENCAR mice generated significant amounts of superoxide when stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA) in vitro; negligible responses were observed for MPs derived from relatively resistant B6C3F1 mice. We hypothesized a similar strain-dependent secretion of transforming growth factor-alpha (TGF-alpha) by TPA-stimulated MPs. TGF-alpha secreted by MPs was quantitated by competitive enzyme-linked immunosorbent assay. After 72 h (maximal secretion), for MPs derived from B6C3F1 mice, in vitro exposure to 10 microgram/mL lipopolysaccharide (LPS; non-lipid-A-detoxified) resulted in maximal induction (708 pg/mL), in vivo exposure to intraperitoneally (i.p.) administered TPA (2 micrograms/mouse) alone resulted in a minimal response (32 pg/mL), and prior in vivo exposure to TPA significantly inhibited (more than 90% suppression) the LPS-stimulated MP response in culture (i.e., to 62 pg/mL). Although significant amounts of TGF-alpha could be detected in both SENCAR- and B6C3F1-derived MPs (i.e., approximately 2-3 ng/5 x 10(6) cells), SENCAR MPs did not secrete TGF-alpha in response to either TPA or LPS. In addition, the use of the semiquantitative reverse transcription-polymerase chain reaction to detect TGF-alpha-specific mRNA did not support the strain dependency observed for LPS-stimulated TGF-alpha secretion, i.e., detectable transcripts were observed in MP RNA derived from both strains. In conclusion, although TPA itself demonstrated negligible effects on TGF-alpha expression in murine MPs, prior in vivo exposure inhibited LPS-stimulated transcriptional activation and intracellular TGF-alpha production. The negligible TGF-alpha secretion determined for LPS-stimulated SENCAR-derived MPs suggested the possibility of a strain-specific defect in the posttranslational processing of the proTGF-alpha molecule.

Assessment of microbial growth in intravenous immune globulin preparations.

The ability of intravenous immune globulin (IVIG) products to support bacterial and yeast growth was studied. Microtiter plates containing preparations of eight commercially available IVIG products were inoculated with 10(5) colony-forming units (CFUs) of bacteria per milliliter or 10(3) CFUs of yeast cells per milliliter. The organisms used were Candida albicans, Torulopsis glabrata, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Klebsiella pneumoniae. The plates were incubated at 3, 25, or 37 degrees C for seven days. For each organism and each temperature, a total of 16 identical wells were studied per preparation. Optical density was measured at 24-hour intervals to determine bacterial growth; yeast growth was determined visually. None of the IVIG preparations supported bacterial growth at any temperature over the seven-day period. No preparation supported visible yeast growth at 3 degrees C; however, most of the preparations did support yeast growth at 25 and 37 degrees C. The failure of the IVIG preparations to support bacterial growth at all temperatures and yeast growth at 3 degrees C suggests that a reconsideration of recommended expiration dates for IVIG products may be warranted.

Patients' perceptions of pharmaceutical services offered by an ambulatory clinic pharmacy.

The importance that patients place on various patronage motives and service offerings of an ambulatory pharmacy associated with a university hospital was studied. Questionnaires were distributed to 193 patients and 8 pharmacists employed at the pharmacy. The patient questionnaire contained a list of 13 patronage motives and 18 service offerings. Respondents rated the importance of each patronage motive in their decision to visit the pharmacy and their view of the importance of each pharmaceutical service offering on an anchored scale (1 = not important, 5 = very important). The pharmacist questionnaire included the 18 service offerings. Pharmacists rated their perceptions of the importance patients place on each service. The response rates were 52.8% for patients and 100% for pharmacists. Patients indicated acceptance of insurance plan, availability of prescription medication, and presence of a knowledgeable pharmacist as the most important patronage motives. Ability to call in refills by telephone and various interactions with the pharmacist were identified as the most important service offerings. The results showed congruence between the pharmacists' perceptions of important patient services and the importance patients actually place on the services. Understanding the importance of patronage motives and service offerings is necessary in the development of marketing activities to attract new patients and retain current patients.

Induction of superoxide by 12-O-tetradecanoylphorbol-13-acetate and thapsigargin, a non-phorbol-ester-type tumor promoter, in peritoneal macrophages elicited from SENCAR and B6C3F1 mice: a permissive role for the arachidonic acid cascade in signal transduction.

Local production of reactive oxygen intermediates, e.g., superoxide anion, by tumor promoter-stimulated inflammatory macrophages (MPs) may contribute significantly to tumor development in classical models of two-stage chemical-induced carcinogenesis in murine skin. In the studies reported herein, peritoneal MPs elicited from phorbol-ester-sensitive SENCAR mice demonstrated a time- and dose-dependent release of superoxide anion (4-6 nmol/10(6) cells) when stimulated by 200 nM 12-O-tetradecanoylphorbol-13-acetate (TPA) in vitro; MP superoxide response was significantly inhibited (50-70%) by preincubation with 40 microM 1-(5-isoquinolinyl-sulfonyl)-2-methylpiperazine (H-7), a protein-kinase inhibitor. Alternatively, TPA-stimulated MPs derived from relatively resistant B6C3F1 mice generated negligible superoxide under the same conditions. A similar strain-dependent induction of superoxide was observed when MPs were stimulated with thapsigargin (TG), a tumor promoter previously shown to act independently of protein kinase C (PKC). TG-stimulated SENCAR MPs released a significant amount of superoxide (2-3 nmol/10(6) cells) that was not inhibited by H-7; MPs from B6C3F1 mice demonstrated negligible stimulation by TG. Preincubation of SENCAR MPs with 100 microM dibromoacetophenone, an inhibitor of phospholipase A2, completely suppressed the superoxide induced by TPA and TG stimulation. Like TPA, 50 microM 1-oleoyl-2-acetylglycerol, a diacylglycerol analogue and PKC activator, also induced a significant amount of superoxide from SENCAR MPs only. In parallel with the superoxide findings, TPA and TG stimulated significantly greater [3H]arachidonic acid release from prelabeled SENCAR MPs (a 32% and 48% increase, respectively, over unstimulated controls) relative to MPs from B6C3F1 mice. Two-dimensional gel-electrophoretic analysis indicated that TPA-induced phosphorylation of a 47-kDa protein (a presumed substrate for PKC previously linked to NADPH oxidase activation in guinea pig and human polymorphonuclear leukocytes) occurred in MPs from both SENCAR and B6C3F1 mice. Therefore, arachidonic acid production may be a common biochemical pathway by which phorbol-ester--and non-phorbol-ester--type tumor promoters activate MPs in SENCAR mice; such a response may be "permissive" for additive (or synergistic) interactions with PKC-driven signal pathways.

3-Methylindole-induced splenotoxicity: biochemical mechanisms of cytotoxicity.

3-Methylindole (3-MI) is a pneumotoxic metabolite of L-tryptophan that can form in the digestive tracts of humans and ruminants as a result of microbial protein metabolism. Alternatively, human lungs can be directly exposed to 3-MI formed during protein pyrolysis and inhalation of tobacco smoke. 3-MI has been shown to cause acute lung injury in both ruminants and rodents. The present studies demonstrate that the spleen is also a target for 3-MI-induced toxicity. A dose-dependent decrease in splenic weight (24-75%) and nucleated splenic cell number (22-68%) was observed 24 hr after intraperitoneal injection of 3-MI (50-300 mg/kg) to intact and adrenalectomized rats. These findings were associated with significant alterations in splenic histopathology. Mice appeared less affected by 3-MI than rats as no splenotoxicity was observed at doses less than 200 mg/kg. Other mono- and dimethyl-substituted indoles did not decrease mouse spleen cell numbers when administered in vivo. Phenobarbital pretreatment in vivo protected against 3-MI-induced splenotoxicity, suggesting a role for cytochrome P450-mediated metabolism of 3-MI in the splenotoxicity of this compound. Exposure of rat or mouse splenic cells to 3-MI (1 mM) in vitro resulted in toxic changes over 24 hr. However, equimolar concentrations of the structurally related mono- and dimethylindoles were also toxic in vitro, and preincubation with a variety of inhibitors of cytochrome P450 or prostaglandin synthase in vitro failed to protect against 3-MI-mediated toxicity to splenic cells in culture. These results suggest mechanisms of 3-MI splenotoxicity also exist that do not require bioactivation, and indicate a possible role for alkylindoles in suppression of immune function.

3-Methylindole-induced splenotoxicity: functional analysis of immune parameters and lymphocyte phenotyping by flow cytometry.

In this laboratory, 3-methylindole (3-MI), a pneumotoxic metabolite of L-tryptophan that forms in the digestive tract of humans and ruminants, has been demonstrated to be toxic to rat and mouse splenic cells both in vitro and in vivo. The present studies examine whether the reduction in nucleated splenic cells is associated with alterations in: (1) immune functioning (e.g., B and T cell mitogenic responses to lectins), (2) natural resistance (e.g., natural killer (NK) activity and cytokine release from macrophages (MPs)), or (3) the relative percentages of B and T cells in the remaining cells as determined by flow cytometric phenotyping. A dose-dependent decrease in splenic weight (24-46%) and nucleated cell numbers (54-73%) was observed 24 hr after intraperitoneal (ip) administration of 100-300 mg/kg 3-MI to B6C3F1 mice. At a dose of 300 mg/kg, the blastogenic response of splenic lymphocytes to 1 microgram/ml phytohemagglutinin, a T cell mitogen, was reduced 37 and 64%, and NK activity was reduced 20 and 60%, in rats and mice, respectively. Following exposure to 400 mg/kg 3-MI, interleukin-1 and tumor necrosis factor production by lipopolysaccharide-stimulated rat splenic MPs was decreased 58 and 38%, respectively. Despite the reduction in total nucleated cell number in 3-MI-treated mice, the percentages of splenic B and T cells remained the same. These findings indicate that, in addition to its toxicity to splenic cells, 3-MI can significantly impair the functioning of the remaining viable cells. The potential importance of these functional changes for alterations in host resistance in rodents exposed to 3-MI or other alkylindoles is unknown.

Induction of granulocyte-macrophage colony-stimulating activity by 12-O-tetradecanoylphorbol-13-acetate in SENCAR and B6C3F1 mice.

Previous studies in this laboratory and others have indicated that 12-O-tetradecanoylphorbol-13-acetate (TPA), the most potent skin tumor promoter known, evokes significantly greater inflammatory responses in phorbol ester-sensitive (SENCAR) mice compared to strains (e.g. C57BL/6 and B6C3F1) that are relatively resistant to the outgrowth of skin tumors in two-stage chemically induced carcinogenesis protocols. In the studies reported herein, subchronic topical application of TPA at doses relevant to two-stage protocols induced serum granulocyte-macrophage colony-stimulating activity (GM-CSA) in both SENCAR and B6C3F1 mice; however, the increase in SENCAR mice was significantly greater than that observed in the relatively resistant B6C3F1 strain (5-fold versus a 2-fold increase respectively). The greater increase in serum GM-CSA observed in SENCAR mice was correlated with a 31% increase in the number of splenic leukocytes that lacked both B and T cell surface markers (i.e. double-negative cells), a presumed GM progenitor cell; no significant increase in the relative percentage of such cells was observed in B6C3F1 mice. Alternatively, significant decreases in splenic T lymphocytes (23 and 32% in SENCAR and B6C3F1 respectively) were observed in both strains of TPA-treated mice and may, in part, account for the previously observed decreases in splenic cell blastogenic response to the T cell mitogen phytohemagglutinin (PHA). In vitro incubation of splenic cells from SENCAR mice with 0.01-1.0 microM TPA led to significantly greater increases in colony formation relative to splenic cells isolated from B6C3F1 mice; therefore, differences in the biochemical responsiveness between strains may occur at the level of signal transduction in splenic GM progenitor cells. In conclusion, these studies indicated that strain-dependent differences in the systemic inflammatory response following topical application of TPA may result from direct stimulation of splenic GM precursor cells by TPA and/or may occur, indirectly, through the release of cytokines [e.g. GM colony-stimulating factor (GM-CSF)] by induced epidermal (or other) cells.

Induction of interleukin-1 and tumor necrosis factor by 12-O-tetradecanoylphorbol-13-acetate in phorbol ester-sensitive (SENCAR) and resistant (B6C3F1) mice.

12-O-tetradecanoylphorbol-13-acetate (TPA), the most potent skin tumor promoter known, evokes significant inflammatory responses in mouse skin after topical application. Infiltrating inflammatory cells have been hypothesized to contribute to genetic damage in epidermal cells through the generation of reactive oxygen intermediates (ROIs), thus facilitating the development of tumors. Interleukin-1 (IL-1) and tumor necrosis factor (TNF), small mol. wt cytokines produced by macrophages (MPs), are known to have important roles in the inflammatory process. Lipopolysaccharide (LPS)-triggered release of IL-1 and TNF was determined in culture supernatants of splenic MPs from phorbol ester-sensitive (SENCAR) and resistant (B6C3F1) mice following topical application of 8 micrograms of TPA twice in one week. The findings reported herein indicated that topical application of TPA primed splenic MPs from both SENCAR and B6C3F1 mice in a quantitatively similar manner for the production of IL-1 and TNF; in addition, the release of IL-1 and TNF by splenic MPs from control (naive or acetone-dosed) SENCAR and B6C3F1 mice in response to LPS-triggering in vitro was not significantly different. Therefore, the production and release of these cytokines by activated MPs does not correlate with the reported strain-dependent susceptibilities to TPA-induced inflammation and/or tumor promotion.

Induction of suppressor macrophages by 12-O-tetradecanoylphorbol-13-acetate in phorbol ester-sensitive (SENCAR) and resistant (B6C3F1) mice.

Following topical application of 8 micrograms 12-O-tetradecanoylphorbol-13-acetate (TPA) twice in one week, the ability of splenic macrophages (M phi s) isolated from phorbol ester-sensitive (SENCAR) and resistant (B6C3F1) mice to suppress the phytohemagglutinin (PHA)-induced lymphocyte blastogenesis and NK activity mediated by spleen cells from naive animals was determined. In B6C3F1 mice, suppression of lectin-induced lymphocyte blastogenesis was mediated by M phi s from TPA-dosed animals. Alternatively, in TPA-dosed SENCAR mice, induction of M phi s suppressive to lectin responses was not apparent. In addition, suppressor M phi s did not mediate the decreased splenic natural killer (NK) activity that is characteristically observed in TPA-dosed SENCAR mice. Therefore, it is proposed that the decreased PHA responsiveness and NK activity observed in vivo in TPA-dosed SENCAR mice may be the result of a decreased proportion of lectin-responding T cells and NK cells in the spleen as a result of proliferation of inflammatory cell precursors.

Anthralin, a non-phorbol tumor promoter, fails to inhibit metabolic cooperation in mutant human fibroblasts, but inhibits phytohemagglutinin-induced lymphocyte blastogenesis in vitro.

Two (among many) of the hypotheses put forward to explain mechanisms of action of tumor promoters are: (1) immunosuppression of the host; and (2) inhibition of intercellular junctional communication. Murine spleen cells were exposed for 30 min to various concentrations of anthralin (1,8-dihydroxy-9-anthrone), a polyphenolic non-phorbol promoter, and 1,8-dihydroxyanthraquinone (1,8-DHAQ), an inactive congener. Phytohemagglutinin (PHA)-induced T cell blastogenesis, an indicator of lymphocyte function, was then assessed in vitro. Exposure to anthralin resulted in a concentration-dependent suppression of lymphocyte proliferation with complete suppression occurring at 1 microM. The inactive congener, 1,8-DHAQ, failed to suppress lectin-induced blastogenesis at concentrations up to 10 microM. Dithiothreitol (DTT), a sulfhydryl (SH) compound, failed to protect against the suppression of lymphocyte function by anthralin. In addition, anthralin failed to inhibit in vitro microtubule assembly, a SH-dependent process, in a crude rat brain extract. Finally, unlike 12-O-tetradecanoylphorbol-13-acetate (TPA), the most potent skin tumor promoter known, anthralin failed to inhibit metabolic cooperation between mutant human fibroblasts as assayed by [14C]citrulline incorporation. In summary, the data suggest that anthralin may act as a tumor promoter by suppressing immune parameters, a property which is shared by the phorbol esters.

Predicting caffeine plasma concentrations resulting from consumption of food or beverages: a simple method and its origin.

Multiple dosage regimens for therapeutic agents are commonly comprised of a constant dosing interval and a constant dose size. This is not true for the ingestion of a pharmacologically active agent that is a component in a dietary source. Caffeine is contained in foods and beverages that are regular components of the diet for many people. Because daily intake is unsystematic, a computer program was written to simulate caffeine plasma concentration-time courses following ingestion of variable amounts on irregular schedules. Literature values for caffeine pharmacokinetics, for the caffeine content in various foods and beverages, and for consumer habits were employed to simulate various caffeine plasma concentration-time courses. By searching for predictable traits in a wide variety of plasma concentration-time courses representing normal adults, a simple noncomputer method was developed to allow individuals to estimate caffeine plasma concentrations based on personal intake habits. Changes in the time courses due to smoking, oral contraceptive use, and liver disease, all of which alter caffeine pharmacokinetics, were also examined.

Modulation of natural killer activity by 12-O-tetradecanoylphorbol-13-acetate and benzoyl peroxide in phorbol ester-sensitive (SENCAR) and resistant (B6C3F1) mice.

Following two weeks of topical application of 12-O-tetradecanoylphorbol-13-acetate (TPA) at 2, 4 and 8 micrograms/mouse on alternate days (7X total) or benzoyl peroxide (BZP) at 10, 20 and 40 mg/mouse, natural killer (NK) activity was determined in local (lymph nodes draining the lower dorsal region) and systemic (spleen) lymphoid tissue in phorbol ester-sensitive (SENCAR) and resistant (B6C3F1) mice. SENCAR mice, sensitive to tumor induction by TPA in two-stage chemical-induced carcinogenesis protocols, demonstrated suppression of NK activity in the spleen (no significant change in lymph nodes) and substantial dose-dependent increases in cell numbers in these organs after topical exposure to TPA. B6C3F1 (C57BL/6 X C3H F1) mice, reported to be resistant to TPA-induced promotion, demonstrated significant increases in NK activity in lymph nodes/spleen with an increase in cell numbers in the draining nodes only. Unlike the C57BL/6 parental strain, B6C3F1 mice are also reported to be resistant to promotion with BZP. Significantly, studies in this laboratory indicated that B6C3F1 mice dosed with BZP demonstrated increased NK activity in the spleen as was observed after dosing with TPA. These data suggest that alterations in NK activity as a result of exposure to tumor promoters may, in part, account for the resistance of particular strains of mice to tumor development. In both SENCAR and B6C3F1 mice, the blastogenic response of spleen cell suspensions isolated from TPA-dosed animals to phytohemagglutinin (PHA), a T cell lectin, was suppressed in a dose-dependent manner; BZP had no effect on spleen cell responses in either strain. Blastogenic responses of lymph node cells to PHA were enhanced in both strains of mice after topical application of TPA and BZP. Therefore, alterations in lymphoid cell responsiveness to PHA appeared unrelated to the reported sensitivities of SENCAR and B6C3F1 mice to tumor promotion.

Iodoacetic acid and related sulfhydryl reagents fail to inhibit cell-cell communication: mechanisms of immunotoxicity in vitro.

The present study was undertaken to examine the effects of iodoacetic acid, a non-phorbol tumor promoter, on metabolic cooperation between mutant human fibroblasts as measured by [14C]citrulline incorporation. Other thiol-reactive polyphenolic compounds such as hydroquinone and 2-hydroxyestrone were also examined. 12-O-Tetradecanoyl phorbol-13-acetate (TPA), a potent skin tumor promoter, inhibited the cell-cell communication by more than 60% at 20 ng/ml. However, iodoacetic acid, hydroquinone, and 2-hydroxyestrone, had no effect on the process even at cytotoxic concentrations. Induction of intercellular contact (agglutination) among lymphocytes during the course of phytohemagglutinin (PHA)-induced blastogenesis was monitored turbidometrically at 620 nm. Hydroquinone and 2-hydroxyestrone suppressed the PHA-induced lymphocyte agglutination at 1-2 microM in vitro concentrations while iodoacetic acid was devoid of any effects at concentrations up to 100 microM. Hydroquinone and 2-hydroxyestrone concomitantly suppressed PHA-induced lymphocyte blastogenesis at 1-2 microM in vitro concentrations while the suppression by iodoacetic acid was significant at 10 microM. All 3 compounds failed to disrupt microtubule assembly, a sulfhydryl-dependent process, in a rat brain crude extract. However, p-benzoquinone, an oxidation product of hydroquinone, did inhibit the process at 1 mM. In summary, these studies suggest that, unlike TPA, thiol-reactive non-phorbol tumor promoters and polyphenolic compounds do not inhibit cell-cell communication between mutant human fibroblasts. Although the compounds demonstrate diverse molecular mechanisms of action, they all inhibit in vitro immune functions suggesting that immunosuppression may play a role in tumor promotion.

Modulation of lectin-stimulated lymphocyte agglutination and mitogenesis by estrogen metabolites: effects on early events of lymphocyte activation.

Pharmacological doses of estrogens such as 17-beta estradiol (17-beta E) and diethylstilbestrol (DES) suppress cell-mediated immunity in vivo. In this report, we investigated the direct in vitro effects of 17-beta E and its major metabolites on lymphocyte proliferation in response to the T cell lectin phytohemagglutinin (PHA). PHA-induced lymphocyte agglutination, an early event indicative of active, cytoskeletal-dependent membrane alterations, was monitored in conjunction with blastogenesis. Without exception, the effects of individual estrogen metabolites on the PHA-induced agglutination occurring within minutes were accompanied, at every concentration of compound, by equivalent effects on the blastogenic response of activated cells measured after several days. This observation suggested a role for estrogens in modulating lymphocyte activation at the cell surface rather than through cytosolic receptor-mediated events. As suggested by previous studies with quinone metabolites of benzene, the catechol estrogen metabolite 2-OH estrone (2-OH E) was significantly more potent than the parent compound at suppressing lymphocyte proliferation in vitro and in vivo.

Modulation of nonspecific cell-mediated growth inhibition by estrogen metabolites.

Chronic exposure of mice to estrogens such as 17-beta estradiol and diethylstilbestrol inhibits natural killer cell-mediated cytotoxicity in vivo. In this report, we investigated the direct in vitro effects of 17-beta estradiol and its major metabolites on nonspecific effector cell function measured as the ability of naive lymphocytes to inhibit the growth of the YAC-1 lymphoma, a classical natural killer-sensitive target cell. Without exception, the effects of individual estrogen metabolites on the growth inhibitory properties of these cells were accompanied, at every concentration of compound, by identical effects on the blastogenic response of lymphocytes to the T cell lectin phytohemagglutinin. These observations suggested membrane-mediated immunomodulation of lymphocyte function by estrogen metabolites. As suggested by previous studies with quinone metabolites of benzene, the catechol estrogen metabolite 2-OH estrone was significantly more potent than the parent compound at suppressing lymphocyte functions in vitro; however, dosing regimens of 2-OH estrone that suppressed blastogenic response in vivo failed to inhibit nonspecific cell-mediated growth inhibition.

Modulation of lymphokine-induced macrophage activation by estrogen metabolites.

Pharmacological doses of estrogens such as 17-beta estradiol (17- beta E) and diethylstilbestrol (DES) activate macrophages in a thymic-dependent manner in vivo. In this report, we investigated the direct in vitro effects of 17- beta E and its major metabolites on macrophage activation in response to lectin-stimulated lymphocyte supernatants containing macrophage-activating factor (MAF), a T cell lymphokine (LK). Activation was measured in terms of macrophage cytostasis against cultured tumor cells. As suggested by previous studies with quinone metabolites of benzene, the catechol estrogen metabolite 2-OH estrone (2-OH E) was the most potent metabolite at suppressing LK-induced macrophage activation. However, if macrophages were first LK-induced, and then exposed to estrogens before addition of tumor cells, then all the estrogens, including 2-OH E, enhanced cytostasis. These observations suggested membrane-mediated immunomodulation of macrophage function by estrogen metabolites and, indirectly, a role for the thymus in these effects via the maintenance of a mature, LK-producing T cell population necessary for macrophage activation.

Soluble immune response suppressor (SIRS) inhibits microtubule function in vivo and microtubule assembly in vitro.

Soluble immune response suppressor (SIRS) is a product of concanavalin A-stimulated murine T cells that, when activated or oxidized by macrophages or H2O2 (SIRSox), suppresses in vitro immune responses and inhibits cell division by normal and neoplastic cells. SIRSox is inactivated by a variety of electron donors, which suggests that SIRSox may be an oxidizing agent. Incubation of lymphocytes with SIRSox, but not with SIRS, partially reversed concanavalin A-mediated inhibition of capping of membrane immunoglobulin on B cells, and disrupted the cytoplasmic array of microtubules visualized by fluorescence microscopy. SIRSox also inhibited microtubule assembly in vitro in a concentration-dependent manner. Inactivation of SIRSox by dithiothreitol prevented SIRSox-mediated reversal of inhibition of capping and inhibition of microtubule assembly. These results reveal a pattern of SIRSox activity similar to sulfhydryl-dependent cytoskeletal disrupting agents (e.g., N-ethylmaleimide, cytochalasin A, p-benzoquinone), and suggest that SIRSox-mediated suppression of proliferation may involve interference with sulfhydryl-dependent cytoskeletal events critical for cell division.

Phytohemagglutinin-induced acquisition of T-cell surface markers by rat bone marrow precursor cells in the absence of the thymic microenvironment.

Two monoclonal antibodies specific for different rat T-cell subpopulations, the anti-helper-T-cell antibody, W3/25, and the OX8 suppressor cell antibody were used to investigate lectin-stimulated T-lymphocyte differentiation of F-344 rat bone marrow cells in culture. Cytofluorometric analysis of freshly isolated lymphocytes from thymus and spleen revealed that these tissues contained both W3/25- and OX8-positive populations but differed with respect to the number of cells and receptor density distribution. By contrast, bone marrow-derived lymphocytes exhibited negligible W3/25- or OX8-associated fluorescence. However, several days after stimulation of bone marrow lymphocytes with phytohemagglutinin (PHA), cells appeared bearing these markers. Two-parameter histogram analysis of light scatter measurements with cell surface immunofluorescence indicated that this phenomenon represented the appearance of a new population of cells, presumably mature T cells, bearing an increased density of marker. These findings suggest an induction of differentiation of bone marrow T precursor cells by nonthymic factors (PHA) since lymphocytes lacking mature T-cell marker expression developed this characteristic after several days in culture.