In vitro erythrocidal activity of activated spleen cells from young and old mice.

We have recently reported that activated mouse spleen mononuclear cells (MNCs) efficiently lyse autologous erythrocytes in vitro (Saxena and Chandrasekhar, 2000). In the present study, we have investigated erythrocyte-depleting ability (EDA) of spleen MNCs from young and old mice. Time kinetics of survival of erythrocytes in mitogen-activated spleen cell cultures indicated that the erythrocyte depletion was significantly faster in young spleen cell cultures than in the old. Poorer EDA of old MNCs was in spite of the fact that the susceptibility to lysis actually increased in erythrocytes from old mice. Erythrocytes opsonized by a hamster anti mouse Fas monoclonal antibody, were destroyed with a much greater efficiency by young MNCs, whereas the corresponding effect of opsonization was only moderate for old MNCs. Depletion of macrophages from MNC preparations by plastic adherence as well as carbonyl-iron and magnet treatment had a marginal if any effect on EDA of young and old mouse MNCs, indicating that a lower lymphocyte-associated erythrocidal activity as one of the factors responsible for overall lower EDA associated with spleen derived MNCs of old mice.

Cytolytic activity of mitogen activated old and young mouse spleen cells against tumor target cells expressing high or low levels of Fas antigen.

Sensitivity of Fas expressing tumor cells (high levels in Hut78 & Jurkat; low levels in P815) toward the cytotoxic Con-A (5 microg/ml) activated spleen cells from young (12 to 16 week old males) and old (2 year old males) mice were studied. The spleen cells from young mice activated for a day showed high levels of cytotoxic activity against Hut78 and Jurkat cell lines but not against P815 cells. The cytotoxic activity against P815 cells were detected in the spleen cells from old but not young mice following a longer period of Con-A activation (three days). Comparable levels of cytotoxic activity against Hut78 and Jurkat cells were observed in the spleen cells from both young and old mice following three days of activation. Treatment of Hut78 cells with anti-Fas antibody affected the tumor cells become resistant against the cytotoxic activity of the spleen cells from young mice in a dose dependent manner however P815 cells were not affect by the anti-Fas antibody treatment. These results show that there are differences in the sensitivity of target tumor cells toward Con-A induced cytotoxic spleen cells from young and old mouse. Mitogen-induced cytotoxic lymphocytes from young mouse spleen appear to kill targets through mechanisms involving Fas antigen, specially, in early stage (1 day) of activation. Old mouse spleen cells generated high levels of cytotoxic cells in later phase (3 days), which appear to kill through Fas-unrelated mechanisms.

Serum antibodies to HIV-1 are produced post-measles virus infection: evidence for cross-reactivity with HLA.

Convalescent sera obtained from patients who were recently recovered from an acute measles virus infection were tested for the presence of anti-HIV-1 antibodies by Western blot analysis. While 16% (17/104) of control sera displayed reactive bands to a variety of HIV proteins, 62% (45/73) of convalescent sera demonstrated immunoreactive bands corresponding to HIV-1 Pol and Gag, but not Env antigens. This cross-reactivity appears to be the result of an active measles infection. No HIV-1 immunoblot reactivity (0/10) was observed in sera obtained from young adults several weeks after a combined measles, mumps, and rubella (MMR) vaccination. Interestingly, examination of anti-HLA typing sera specific for either class I and class II molecules revealed that 46% (19/41) of these sera contained cross-reactive antibodies to HIV-1 proteins. Absorption of measles sera with mixed lymphocyte reaction (MLR)-activated lymphocytes and/or HIV-1 recombinant proteins significantly decreased or removed the presence of these HIV-1-immunoreactive antibodies. Together, these findings suggest that the immune response to a natural measles virus infection results in the production of antibodies to HIV-1 and possibly autoantigens.

Immunological aspects of aging and malnutrition: consequences and intervention with nutritional immunomodulators.

As knowledge of molecular and cellular mechanisms of development and aging is elucidated, the need to understand the relationships among tissues, organ systems, health habits, nutrition, physical activity, and environmental factors on successful aging becomes more explicit. Progress in our understanding of how the immune system functions and responds with other factors, such as aging and nutrition, is spawning significant inroads to achieving a successful old age.

HIV infection and aging: mechanisms to explain the accelerated rate of progression in the older patient.

Age is an important predictor of progression in HIV infections. Not only do older individuals' develop AIDS more rapidly than younger persons, they die more quickly after developing an AIDS-defining illness. While the elderly have higher morbidity and mortality rates from viral and bacterial infections, the mechanism(s) responsible for the more rapid progression of HIV infection in older individuals has not been described. Our results demonstrate that the destruction of T cells in both young and old HIV infected patients progresses at the same rate. HIV 1-infected cells from older individuals do not appear more susceptible to immune mediated destruction. The more rapid progression appears due to an inability of older persons to replace functional T cells that are being destroyed. These findings suggest that improved survival in older HIV infected individuals will require more aggressive antiretroviral therapies as well as continued research to identify and preserve immune system elements that control the virus.

Antibody to human MHC class I inhibits SIVsmmPBj1.9-induced proliferation of pigtailed macaque lymphocytes.

Previously we have shown that the simian immunodeficiency virus SIVsmmPBj1.9, a molecular clone of SIVsmmPBj14, induces proliferation of human peripheral blood mononuclear cells (PBMC). We have extended this observation to show that SIVsmmPBj1.9 induces proliferation of PBMC from pigtailed macaques. This proliferative response was markedly inhibited by mAbs against human class I MHC, class II MHC and CD4 antigens, and partially inhibited by mAbs against integrin beta 2 subunit (CD18) and LFA-1 (CD11a). However, these antibodies differed in their ability to inhibit in vitro viral infectivity of PBMC. While anti-CD4, MHC class II, and LFA-1 strongly inhibited viral infectivity, antibodies to MHC class I demonstrated little effect on viral infectivity. A control antibody (PLM2) against porcine CD18 inhibited neither virus-induced proliferation nor viral infectivity. Based on these results, we suggest that SIVsmmPBj1.9-induced proliferation requires the participation of class I MHC, class II MHC and CD4 molecules. In addition, the observation that anti-class I MHC Ab inhibited proliferation of macaque PBMC induced by mitogen (PHA) and bacterial superantigens, such as Staphylococcus enterotoxin A and toxin shock syndrome toxin-1, suggests that SIVsmmPBj1.9 also contains a viral superantigen similar to that previously demonstrated in SIVsmmPBj14.

Age-dependent resistance factors in the pathogenesis of foodborne infectious disease.

With increasing age there is an increase in both the incidence as well as the mortality due to many infectious illnesses, and foodborne infectious disease is no exception. A review of the pertinent literature identified studies concerning foodborne disease caused by infectious agents in the elderly, as well as those factors that could account for the increase in morbidity and mortality seen in the elderly due to foodborne infections. The published information suggested that the basis for the increased incidence, severity and risk of death of many foodborne infectious diseases in elderly persons is related to factors such as reduced gastric acidity, a higher prevalence of underlying medical disorders (co-morbidity factors), and immune system changes that result in a less effective host defense against infectious agents. The greater risk of foodborne disease experienced by elderly persons results from the contribution of non-immune and immune mediated factors. Due to the growing number of persons over the age of 65 years in the United States, foodborne disease in this age group will continue to be an important source of illness and death in the population.

Immunoglobulin heavy chain junctional diversity in young and aged humans.

The causes of observed deficiencies to the humoral immune response in aged humans are unknown. Since a major source of antibody diversity is generated at the VH-D-JH junctional regions of the immunoglobulin heavy chain, we determined whether differences in junctional diversity are manifested with aging. We compared the CDR3 regions of IgM heavy chain transcripts isolated from young adult and aged humans. A PCR assay that measures CDR3 length in the majority of mu-heavy chains showed the same average size and normal range of CDR3 length in aged individuals as observed in young adults. To characterize the features of junctional diversity of aged adults in more detail, we determined the CDR3 sequences of a subset of the mu-heavy chain repertoire that utilizes members of the VH 5 family. In general CDR3 length, D family usage, and JH gene usage were similar in aged compared to young adults. Thus, in contrast to dramatic changes in heavy chain junctional diversity associated with fetal to adult development, no major differences were found between young and aged adults. Since the CDR3 repertoire generated in aged individuals appears to be as diverse as that observed in younger adults, the decline in humoral immunocompetence with aging cannot be attributed to a restriction in heavy chain junctional diversification processes.

Bcl-2 transfection protects Hut78 cell line from different types of cytotoxic effector cells.

The human T lymphoma cell line Hut78 was transfected with Bel-2 gene or with control G418 Neomycin resistance-conferring plasmid. Bcl-2 transfected and Neomycin selected Hut78 cells expressed about ten-fold greater Bcl-2 protein than the neo-transfected controls. Susceptibility of Bcl-2-transfected Hut78 cells to human NK cells, human mixed lymphocyte reaction-generated cytotoxic effector cells, and mouse cytotoxic spleen cells generated by immunization with Hut78 cells was examined. In all systems tested, Bcl-2-transfected Hut78 target cells were significantly less susceptible to lysis than the neo-transfected control target cells. These results suggest that in Hut78 cells, Bcl-2 gene product may confer partial resistance to different types of cytotoxic effector mechanisms.

Anti-HLA class I antibody inhibits Staphylococcus enterotoxin A (SEA)-induced proliferation of human PBMC.

The antigen-presenting role of major histocompatibility complex (MHC) Class I molecules in the activation of appropriately restricted T cells is well documented. Now growing evidence indicates that MHC Class I molecules can, in addition, exert a regulatory effect and influence the resulting immune responses. In this report we show that a monoclonal antibody (mAb) directed against a conserved region of the human leukocyte antigens (HLA)-A, -B, and -C was able to inhibit proliferation of human peripheral blood mononuclear cells induced by the superantigen, Staphylococcus enterotoxin A. While anti-HLA inhibition was associated with a decrease in IL-2 receptor (IL-2R) expression, the addition of exogenous IL-2 did not restore the proliferative response in the presence of anti-HLA mAb. The inhibition of DNA synthesis was also associated with a decrease in the expression of the early activation marker CD69. These results suggest a critical role for HLA Class I molecules in the early events of human lymphocyte activation and proliferation as well as in their expression of the IL-2R.

Acquired immunodeficiency syndrome in the elderly.

Recent data from the US show that since 1990 the number of paediatric patients with AIDS is decreasing while the number of patients with AIDS over age 50 years is increasing. To date, little attention has been given to understanding AIDS risk-taking behaviours, clinical presentations, and therapeutic needs of middle-aged and older HIV-infected individuals. Older HIV-infected individuals deteriorate more rapidly than younger patients due to an accelerated loss of CD4+ helper T cells. Despite recognised age-related physiological differences between young and elderly individuals, scant information about drug optimisation for the treatment of AIDS in older individuals is available. More data need to be collected about this group of AIDS patients, and appropriate treatment strategies designed for their special needs.

Does high MHC class II gene expression in normal lungs account for the strong immunogenicity of lung allografts?

Clinical experience has demonstrated that lung allografts are considerably more immunogenic than liver allografts although both organs contain equivalent amounts of lymphoreticular tissue. Northern blot analysis of MHC class II gene expression in various murine organs with I-AB and I-EB gene-specific oligonucleotide probes revealed that MHC class II expression in lungs is semiquantitatively higher than in the liver and other organs with the exception of the spleen. We conclude that this high MHC class II expression strongly suggests that the lymphoreticular tissue in the lungs is in a state of activation. This may be an important reason for the strong immunogenicity of lung allografts.

Concurrent strong tyrosine phosphorylation of a 42,000 MW ERK and a 100,000 MW protein is associated with IL-2 production in human Jurkat T cells.

The tyrosine phosphorylated protein(s) responsible for the signalling for interleukin-2 (IL-2) production has not been clearly defined. In this study, the relationship between IL-2 production and the protein tyrosine phosphorylation pattern of human Jurkat T cells was investigated using phosphotyrosine immunoblotting analysis. With anti-CD3 or anti-CD2 activation the cells showed only a low (anti-CD3) or a moderate (anti-CD2) level of tyrosine phosphorylation of a 42,000 MW external signal-regulated kinase (ERK), which was accompanied by undetectable (anti-CD3) or low level (anti-CD2) IL-2 production. In the presence of phorbol myristate acetate (PMA), large amounts of IL-2 were induced by both anti-CD3 and anti-CD2 stimulation, which was accompanied by strong concurrent tyrosine phosphorylation of the 42,000 MW ERK and a 100,000 MW protein. PMA alone, which induced high levels of tyrosine phosphorylation of the ERK protein, neither induced any detectable IL-2 nor increased the level of tyrosine phosphorylation of the 100,000 MW protein. These observations suggest that concurrent tyrosine phosphorylation of the 42,000 MW ERK and a 100,000 MW protein may be required for IL-2 production.

Age-related effects in T cell activation and proliferation.

Age-associated thymic involution manifests its effects in a variety of ways that are related to a loss of T cell function. These include the appearance of a non-functional subset of T cells that increase in representation with age. Moreover there is a loss of T cell proliferative ability, a decline in the synthesis and release of interleukin-2 (IL-2), a decline in the ability of the T cell to express the IL-2 receptor, and a loss of control activity. This loss of control is demonstrated by the age-related appearance of autoantibodies and an increase in the elaboration of inflammatory cytokines such as TNF, IFN, IL-6, and TGF. A major part of the basis for the loss of T cell function is an inability of the T cell to respond to activation signals that are transmitted through the membrane binding of specific stimulatory signals. Transduction events, differentiation signals, and a loss of control mechanisms are all parts of a complicated picture of age-related immune deficiencies.

Immunomodulation of interleukin-2 by cyclophosphamide: a phase IB trial.

The objective of this phase IB trial was to determine if cyclophosphamide (CY) could enhance the immune effects of interleukin-2 (IL-2), and if it could, was there an optimal immunomodulatory dosage. IL-2 alone at 30 million IU/m2 thrice weekly for 6 weeks or in combination with varying dosages of CY (300, 600, and 1,200 mg/m2) administered 3 days before IL-2 and repeated 3 weeks later was given to consecutive cohorts of patients (at least five per group) with advanced malignancies of varying types. To gauge the immune effects of the treatment, the variation in the amount of lymphokine-activated killer (LAK) cells generated in the peripheral blood mononuclear cells of patients and in a control group of normal volunteers was measured weekly over 7 consecutive weeks. Other immune parameters [natural killer cells (NK), peripheral blood eosinophils and lymphocytes, cell surface markers, soluble IL-2 receptor, and IL-2 antibodies] were also closely followed to study if they correlated with the degree of LAK activity. The group of patients that received low-dosage CY (300 mg/m2) and IL-2 produced the highest and most sustained levels of LAK and NK activity (p < 0.05) when compared with the cohorts receiving IL-2 alone or to those receiving the higher dosages of CY. No other immune parameter showed a significant difference between the groups. Although low-dosage CY does increase the LAK activity seen with IL-2, only randomized clinical trials can determine if this enhancement will improve tumor responses.

Laminin concentrations in serum and cerebrospinal fluid in aging and Alzheimer's disease.

Laminin, a basement membrane protein, and a potent promoter of neurite outgrowth, surrounds all peripheral nerves. It appears in the central nervous system during development and reappears in response to injury. In Alzheimer's disease (AD), there is a progressive loss of neurons in specific areas of the brain along with the presence of an increased number of senile plaques and neurofibrillary tangles. Laminin levels have been shown to be increased in injury, so we undertook to examine levels of laminin by radioimmunoassay (RIA), in cerebrospinal fluid and serum of patients with AD and age-matched controls. No difference in the CSF and serum laminin concentrations was found between Alzheimer's disease and age-matched controls. We found a lack of correlation between severity of clinical dementia and laminin concentrations. Finally, we show that the CSF and serum laminin concentrations increase with age.

Relationship between IL-2 receptor expression and proliferative responses in lymphocytes from HIV-1 seropositive homosexual men.

Previous studies have shown that exogenous IL-2 does not correct the reduction in phytohaemagglutinin (PHA)-induced proliferation of lymphocytes from HIV-1 infected (HIV+) individuals. We investigated the mechanism of this reduction to determine if reduced expression of the complete IL-2 receptor (IL-2R) was responsible. In a series of experiments, PHA-stimulated lymphocytes from a total of 89 HIV- and 93 HIV+ homosexual men from the Baltimore Multicentre AIDS Cohort Study (MACS) were studied to determine the expression of messages for the alpha and beta subunits of the IL-2R, the binding of 125I-IL-2 to high affinity IL-2R, and the effect of IL-2 on cell proliferation. Compared to HIV- donors, PHA-stimulated lymphocytes from most HIV+ donors demonstrated (i) a reduction in high affinity IL-2R expression that correlated with the reduction in the IL-2-induced proliferative response; and (ii) a reduction in expression of both IL-2R alpha- and beta-chain mRNA which may be responsible for decreased high affinity IL-2R expression. However, lymphocytes from some HIV+ individuals had borderline low IL-2-induced proliferation despite normal or elevated expression of high affinity IL-2R. These results suggest that decreased expression of IL-2R may account, at least in part, for the lower proliferative response of cells from HIV+ donors.

Comparison of CD3 and CD2 activation pathways in T cells from young and elderly adults.

The ability of purified T cells to be activated by immobilized anti-CD3 and soluble anti-CD2 monoclonal antibodies (mAbs) was compared using cells from young and old donors. Purified T cells from elderly humans activated with immobilized anti-CD3 mAb incorporated less [3H]thymidine (58,780 vs 92,258 cpm; p < 0.02) into cellular DNA, and secreted less IL-2 into the culture supernatants than did T cells from young donors. In contrast, T cells activated with anti-CD2 mAbs displayed no age-related differences in proliferation or IL-2 production. Anti-CD2 stimulation resulted in equal IL-2 synthesis by cells from young and old donors that was comparable to the amount produced by cells from elderly donors stimulated with immobilized anti-CD3. Northern blot analysis of early cell cycle gene expression by anti-CD2 activated T cells demonstrated no age differences in the expression of p55 IL-2R or c-myc specific mRNA, although T cells from elderly individuals activated with immobilized anti-CD3 showed statistically significant decreases in both mRNAs. T cell receptor beta chain mRNA levels did not differ between cells from young or old donors after activation by either anti-CD3 or anti-CD2. The discordance in proliferative ability, IL-2 secretion, and specific mRNA expression between T cells from elderly donors activated through the CD3-TCR complex or by soluble anti-CD2 mAbs provides additional evidence for a multifactorial causation of age-related T cell proliferative defects, and may indicate that the difference in proliferative ability is, in part, attributable to responsiveness to secreted IL-2.