Multiple roles of CLAN (caspase-associated recruitment domain, leucine-rich repeat, and NAIP CIIA HET-E, and TP1-containing protein) in the mammalian innate immune response.

NAIP CIIA HET-E and TP1 (NACHT) family proteins are involved in sensing intracellular pathogens or pathogen-derived molecules, triggering host defense responses resulting in caspase-mediated processing of proinflammatory cytokines and NF-kappaB activation. Caspase-associated recruitment domain, leucine-rich repeat, and NACHT-containing protein (CLAN), also known as ICE protease-activating factor, belongs to a branch of the NACHT family that contains proteins carrying caspase-associated recruitment domains (CARDs) and leucine-rich repeats (LRRs). By using gene transfer and RNA-interference approaches, we demonstrate in this study that CLAN modulates endogenous caspase-1 activation and subsequent IL-1beta secretion from human macrophages after exposure to LPS, peptidoglycan, and pathogenic bacteria. CLAN was also found to mediate a direct antibacterial effect within macrophages after Salmonella infection and to sensitize host cells to Salmonella-induced cell death through a caspase-1-independent mechanism. These results indicate that CLAN contributes to several biological processes central to host defense, suggesting a prominent role for this NACHT family member in innate immunity.

Involvement of thymic hormones in regulation of the pituitary-adrenal axis in mice.

The effects of thymic hormone thymosin (fraction 5) and tactivin on the adrenal glucocorticoid function were compared in BALB/c mice. An elevation in plasma corticosterone level was found 3 h after i.p. injection of thymosin (1 microgram/mouse) which was possibly caused by an activation of neuroendocrine structures. This appeared plausible because the pretreatment with dexamethasone (10 micrograms/mouse) abolished the effect of thymosin. In contrast, tactivin produced a decrease in plasma corticosterone if administered to mice with high basal level of the hormone. Tactivin added at doses from 0.00064-2 micrograms/ml together with ACTH (1.6 microIU/ml) to isolated adrenal cells hindered the stimulatory influence of ACTH on the production of corticosterone by the adrenal cells. Thus, the thymic hormone thymosin and tactivin showed opposite influences on the adrenal glucocorticoid function which appeared to be mediated through different mechanisms.

Bone marrow and intrathymic precursors of T-cells produce a factor which enhances colony formation in the spleen.

Bone marrow Ig-Thy-1-SC-1- stem cells (precursors of T-lymphocytes, PTL, containing the SC-1 antigen) spontaneously secrete a humoral factor. When bone marrow Ig-Thy-1-SC-1- cells were treated with this factor they became able to form haemopoietic colonies in the spleens of lethally irradiated mice. This new colony-stimulating factor (CSF) is thermostable and has a molecular mass of about 25-30 kDa. Production of the CSF by bone marrow SC-1+Thy-1- cells was stimulated by treatment with the thymus preparation Thymoptin. Such treatment of bone marrow SC-1+Thy-1- cells also induced the production of a suppressor factor (thermolabile, molecular mass about 45 kDa), that reversed the effect of the CSF. The CSF and the suppressor factor are both also produced by cortisone-resistant radioresistant L3T4-Lyt-2-SC-1+ thymocytes (i.e. intrathymic PTL). The regulation of haemopoiesis appears to be a normal function of bone marrow PTL.

Inhibins, activins, and follistatins: gonadal proteins modulating the secretion of follicle-stimulating hormone.

The endocrine system displays highly complex interactions among its components. Excesses or deficiencies of hormone production in one gland may alter the production of hormones by others. Several physiological functions are affected by a balance among hormones acting either together or in sequence. For example, FSH secretion has been demonstrated to be affected by hypothalamic influences upon the anterior pituitary through a specific releasing factor, the decapeptide LRF. This decapeptide stimulates the release of both LH and FSH by the pituitary, and these gonadotropins cause the production of steroids by the testes and the ovaries. Gonadal steroids in the blood act directly upon the anterior pituitary to regulate the output of gonadotropins as originally proposed by Moore and Price in 1932 (3), or act indirectly upon the hypothalamus to adjust the output of pituitary hormones in accordance with the needs of the reproductive system. However, such a simple negative feedback of steroids on the hypothalamic-hypophysial axis cannot account for the differential secretion of FSH observed during the estrus cycle. Therefore, the concept that a gonadal protein, inhibin, specifically regulates FSH secretion was proposed. This concept has now been validated by the isolation and characterization of two forms of inhibin that exert their effects on the pituitary to suppress FSH secretion both in vitro and probably in vivo. Furthermore, the production of inhibin is stimulated by FSH, thus establishing a reciprocal relationship between the release of FSH and inhibin. Since hormones in the body are controlled through interlocking complexes of factors, a variety of secondary factors, in one way or another, may also exert influence on the regulation of FSH secretion. As an example, TGF beta, a protein growth factor found in all tissues, promotes the basal secretion of FSH by the pituitary and enhances FSH-mediated estrogen production by the granulosa cells. It is therefore not surprising that two forms of a novel protein, activin and activin A, isolated from the same FF from which inhibins were isolated, show bioactivities similar to those of TGF beta. These activins are formed as dimers of the two beta-subunits of inhibin, probably as a result of the rearrangement of the gene products. This novel observation that different arrangements of gene products can result in opposite biological activities may thus reflect a wholly different level of control of FSH secretion. If such a phenomenon occurs in other biosystems, it would represent an important form of homeostatic mechanism for controlling biologically active substances.(ABSTRACT TRUNCATED AT 400 WORDS)

Inhibins and activins: chemical properties and biological activity.

The long-sought, nonsteroidal, gonadal inhibitor of the secretion of FSH has been isolated, characterized, and the primary structure in several species (human, porcine, bovine, murine) has been deduced. Inhibins are proteins consisting of two subunits (18-kDa alpha- and 14-kDa beta-subunits) linked by disulfide bridges and two forms of inhibins were observed in human, porcine, and murine, but only one in bovine. Each form of inhibin (A and B) has a common alpha-subunit, but a highly homologous, distinct beta-subunit (beta A and beta B). The beta-subunits and the alpha-subunit are linked to form inhibins A and B which exert an inhibitory effect on basal FSH secretion, but the dimer formed by either two beta A-subunits or two distinct beta A- and two beta B-subunits (homoactivin-A and activin, respectively) possess FSH-stimulating activity. Inhibin secreted in response to FSH from the pituitary originates primarily from the granulosa cells of the ovary and the Sertoli cells of the testes, thus demonstrating a reciprocal feedback relationship.

Thy 1.2 antigen inducing capacity of a calf thymus acid hydrolysate and its fractions.

Splenic null cells of normal mice have been shown to undergo phenotypic induction of Thy 1.2 antigen by various thymic extracts. This experimental model has been employed in characterizing the Thy 1.2 inducing ability of an acid lysate from calf thymus and its various fractions. Incubation of splenocytes from C3H/He mice with unfractionated Thymomodulin induces a dose-response percent increase in the Thy 1.2 antigen bearing cells (9.28 +/- 2.6%, p less than 0.05). Comparable increase appears in fractions 5B (9.46 +/- 0.55%, p less than 0.001) and 5C (8.09 +/- 3%, p less than 0.005), obtained by ultrafiltration and containing peptides of m.w. 600-10,000 d and less than 600 d, respectively. The activity is confined to the acid fraction (6.61 +/- 0.54%, p less than 0.001) isolated by isoelectrofocusing. Control lysate from pig duodenal mucosa was devoid of Thy 1.2 inducing activity. The present findings indicate that Thymomodulin possesses Thy 1.2 inducing capacity on murine null cells and that such activity is maintained and enhanced after various fractionation procedures.

Thymic peptide hormones: basic properties and clinical applications in cancer.

The manuscript will provide an in-depth and critical review of the nomenclature, biochemistry, biological properties, and a summary of published and on-going clinical trials with all reported thymic preparations, including both partially purified thymic factors (e.g., thymosin fraction 5, thymostimulin) as well as purified and synthesized thymic peptides (e.g., thymosin alpha 1, thymulin). Particular emphasis will be placed on which thymic peptides should be categorized as true hormones. In addition, the comparative biochemistry and biological activity in animals will be summarized and contrasted for all the currently available thymic factors. The effects, in vitro of thymic factors, on peripheral blood lymphocytes isolated from normal donors and patients with primary immunodeficiency disorders, autoimmune disorders, and neoplastic disorders will also be reviewed. Finally, a detailed critical summary of the clinical trials performed with each of the thymic preparations will be presented with an emphasis on treatment of patients with cancer.

[Physiological dependency between the hypothalamus and the thymus in Wistar rats. III. Hypothalamic cells cultured in vitro in the presence of Thymus Factor X (TFX) and fresh thymus filtered homogenate].

The studies were carried out on the hypothalamic cells cultured in vitro in the presence of low-molecular proteins (constituting the control): the thymic hormone, known as Thymus Factor X [TFX]; or fresh thymus filtered homogenate prepared from the glands collected from 1 h or 7 d old rats. All the cultures were supplemented with 3H-thymidine. The experiments demonstrated that TFX in when added to the culture caused a decrease 3H-thymidine synthesis in comparison to the control. In other cultures, which were enriched with the fresh thymus filtrated homogenate, especially from 7 d old rats, a high level of thymidine synthesis in the cellular nuclei was observed.

Regulation of theta-antigen expression by agents altering cyclic AMP level and by thymic factor.

Thymic factor, cyclic AMP, and products increasing its cellular level, such as Prostaglandin E1, induce the appearance of the theta-antigen on T-cell precursors whether assessed by a rossette-inhibition assay or a cytotoxic assay after cell fractionation on BSA discontinuous gradiet. Synergism has been demonstrated between cyclic AMPT and TF for that effect. Conversely, decrease of theta expression has been obtained by altering cyclic AMP level in theta-positive cells either increasing it by dibutyryl cAMP treatment or decreasing it by indomethacin treatment. Finally, these data suggest the involvement of cyclic AMP in the regulation of theta expression under thymic hormone control.