Does normal lymphocyte DNA synthesis in response to PHA exclude cell-mediated immunodepression?

The effect of aging on host defences. Implications for therapy

Immunosenescence is a well known physiological phenomenon resulting from reduced efficiency of the immune system in the elderly. It has been studied both in animal models and in humans. In this review attention is focused on T cell responsiveness, since this cell type is both a marker of the immune response and one of the main targets of several drugs. For this latter reason, most studies of the effect of drugs on the immune system have been performed with reference to the effects on T lymphocytes. In the second part of the article experimental data concerning several drugs and drug classes [steroids, calcium antagonists, theophylline, histamine H1- and H2-receptor antagonists, sodium cromoglycate (cromolyn sodium), pirenzepine, rosaprostol, beta 2-mimetics, antibiotics and antibacterials] and immune responsiveness are reviewed. Lastly, the clinical perspectives of pharmacological treatment in aged subjects in relation to immunosenescence are evaluated.

In vivo effect of chronic ethanol abuse on membrane alpha 1-glycoprotein of lymphocytes and immune response to various stimulating agents

Data on the immune status of chronic alcoholic patients are rather conflicting probably due to the interference of liver disease and/or malnutrition on immune function. In order to avoid this kind of interference, peripheral lymphocytes from 12 chronic alcoholic patients in good nutritional status and without heavy liver damage and 15 healthy controls were examined in this study. Lymphocyte functional activity was evaluated by means of response to phytohemagglutinin, calcium ionophore A 23187, and autologous non-T-cells [autologous mixed lymphocyte reaction (AMLR)]. Phenotypical analysis was carried out by the indirect immunofluorescence technique using monoclonal antibodies specific to CD5 (mature T-lymphocytes), CD4 (helper/inducer T-lymphocytes), CD8 (suppressor/cytotoxic T-lymphocytes), glycoproteins, and an immunoglobulin fraction from rabbit directed to membrane alpha 1 acid glycoprotein (AGP) that is involved in T-cell activation process. Our results show significant impairment in AMLR while response to phytohemagglutinin, heterologous non-T-cells and carcinoma ionophore did not differ from controls. No differences were present in circulating T-lymphocytes expressing CD5, CD4, and CD8 on their membrane, whereas AGP-bearing lymphocytes were significantly lower in chronic alcoholics (14.4 +/- 8.6) than in controls (31.9 +/- 8.1; p less than 0.001). These results support the hypothesis of a direct action of alcohol on one of the pathways of lymphocyte activation and the role of the lymphocyte membrane AGP on the AMLR.

Functional study of T lymphocyte responsiveness in patients with dementia of the Alzheimer type

The autologous mixed lymphocyte reaction (AMLR) was used to study T lymphocytes in a group of patients with dementia of the Alzheimer type (DAT) in order to confirm the observation that their T cell proliferation in AMLR was greater than in age-matched controls, and to investigate other pathways of T cell activation, searching for correlations between immunologic and clinical findings in DAT. The mean proliferative response in AMLR was increased in patients with DAT. No differences between patients and age-matched controls were detected when other pathways of T cell activation were investigated. The degree of response in the AMLR varied among patients with DAT. This fits with the suggestion that the disorder may be a heterogeneous syndrome.

Antiallergic drugs and the immune response. Interactions and possible clinical relevance

Since the pharmacological treatment of allergic diseases is used in patients with alteration of the immune response due to atopy and possible concomitant infections, we have investigated the possible effects of such drugs as cromolyn, theophylline, ketotifen, oxatomide, astemizole, fenoterol, pirenzepine, and rosaprostol on the in vitro immune response, in order to obtain experimental data and, as a consequence, clinical conclusions. In a series of investigations by our group and other authors the following immunological parameters have been considered: T cell activation induced by different pathways (i.e. autologous stimulation, PHA, anti-CD3, -CD2 and -CD28 monoclonal antibodies), and lymphokine production (i.e. IL-1, IL-2 and gamma-IFN). For a more detailed experimental model the experiments have been performed both in bulk culture and by using T cell clones derived from the peripheral blood. The results show cromolyn to have an enhancing effect, theophylline and ketotifen a suppressing effect, whereas the remainder show no effect on the immune response. These data are considered and discussed from the aspect of their possible clinical relevance and also in light of the in vivo data previously reported.

Theophylline and the immune response: in vitro and in vivo effects

We analyzed the in vitro and in vivo effects of theophylline on various immunological parameters including proliferation of peripheral mononuclear cells (PMNC) in response to phytohemagglutinin (PHA), anti-T3 and anti-T11 monoclonal antibodies (MAb), PHA-induced interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) production by PMNC, interleukin-1 (IL-1) production by accessory cells, PHA-induced IL-2 production by T-cell clones, and PHA- and anti-T3 MAb-induced DNA synthesis by T cell clones. Results showed that theophylline inhibited PHA- and anti-T3-induced proliferation of both PMNC and T-cell clones, whereas the PMNC proliferation induced by MAb anti-T11 was not affected. The inhibition appeared to be dose-dependent and strictly related to the presence of the drug in the culture. Moreover, PHA-induced IL-2 production by both PMNC and T-cell clones also appeared to be reduced by theophylline. IL-1 production by accessory cells was not affected. These data suggest that the immunological inhibition exerted by theophylline is confined to the T-cell compartment, mainly by acting on structure(s) related to the T3/Ti complex, the primary site for T-cell activation. The alternative pathway of T-cell activation (i.e., via T11 site) seems unaffected. In addition, these results suggest possible clinical relations between the inhibition of the immune response and the plasma levels of the drug reached after a "once daily" or "twice daily" oral ingestion of slow-release theophylline products.

Heterogeneity of immune responsiveness in healthy elderly subjects

We studied a group of healthy elderly subjects (satisfying the SENIEUR Protocol admission criteria), chosen as a model of age-associated immune deficiency on the basis of their reduced skin reactivity to recall antigens. Results show that aged subjects, taken as a whole, display impaired T-cell functions: reduced blastogenetic responses to mitogens, IL-2 production, responsiveness to exogenous IL-2, and percentage of Tac positive blasts. However, the age-associated immune defect shows a wide range of impairment, even in a relatively homogeneous group of anergic/hypoergic subjects. In fact, a considerable proportion of our elderly subjects displays responses comparable with those of adult controls. These observations suggest that (a) immune deficiency is not a characteristic of aging per se; (b) cutaneous delayed hypersensitivity is not a criterion sensitive enough to identify people with age-associated immune deficit; and (c) more than one test is required to evaluate T-cell impairment in aging.

Alpha 1-acid glycoprotein (alpha 1-AGP) on the membrane of human lymphocytes: possible involvement in cellular activation

A glycoprotein termed alpha 1-acid glycoprotein (alpha 1-AGP) is a component of normal human serum; its concentration is often increased in several pathological disorders, including acute inflammation and cancer. Inhibitory effects of alpha 1-AGP on some in vitro T and B cell function assays have been reported but our recent data indicated that alpha 1-AGP is indeed a T cell mitogen at physiological concentrations. The present study was designed to investigate: (a) the relationship between this glycoprotein and two other glycoproteins of the T and B cell membrane, i.e. the T3 and Ia antigens; (b) the ability of lymphocytes to take up exogenous alpha 1-AGP; (c) the different expression of alpha 1-AGP on the T cell membrane upon different activation pathways, i.e., autologous non-T-cells (B cells and monocytes) phytohemagglutinin and anti-T3 monoclonal antibody (MAb) stimulations. The data reported herein show no competition at the membrane level between anti-alpha 1-AGP and anti-T3 or anti-Ia MAbs. In addition, (1) the lymphocytes were able to absorb alpha 1-AGP from the culture medium and (2) the expression of this glycoprotein was enhanced upon T cell stimulation (all three stimulants employed induced an increase of alpha 1-AGP positive T cells), thus suggesting a possible role of this glycoprotein in in vitro T cell activation.

Immunologic dysfunction: simultaneous study of Alzheimer's and older Down's patients

Peripheral blood lymphocytes from Alzheimer's disease patients, older patients (aged 25-59 years) with Down's syndrome and closely age-matched healthy controls were tested in vitro for DNA synthesis in response to stimulation by phytohemagglutinin, pokeweed mitogen and OKT3 monoclonal antibody to T3 antigen. All were significantly decreased in Down's and Alzheimer's patients relative to healthy controls. The autologous mixed lymphocyte reaction (AMLR), unstimulated or stimulated with anti-T3. in the 2 patient groups did not differ significantly from the healthy controls. We also quantified the proportions of the T cells staining positive for surface membrane orosomucoid, and found their levels to be either higher or lower than normal in Down's patients, but not in Alzheimer's patients. These results demonstrate the existence of defective cellular immune functions in both elderly Down's patients and Alzheimer's patients.