Modulation of T lymphocyte differentiation antigens: influence of aging

Cell surface markers, inositol phosphate levels and membrane potential of lymphocytes from young and old human patients

It is well known that most physiological functions change with aging, including the immune response. Data concerning the aging of lymphocyte subpopulations are conflicting. The antigen density of peripheral blood lymphocytes has been determined by fluorescently tagged OKT-3, OKT-4, OKT-8, OKT-11 and OKM1 monoclonal antibodies in a carefully selected aged (over 87 years) population, and compared to that of young subjects. A substantial difference was found in the percentage distribution of OKT8 and OKM1 subsets. The volume of lymphocytes of the elderly population was significantly less than that of the young. The effect of various monoclonal antibodies on phosphatidylinositol breakdown has also been studied. It was found that only OKT3, acting through the CD3 antigen receptor, was able to induce inositol phosphate formation in both young and elderly, although in the latter population this occurred at a lower level. Because the plasma membrane plays a regulatory role in this process, an important and sensitive functional parameter, the membrane potential, was also monitored and influenced by changing the extracellular K+ concentration. The lymphocytes of the elderly population responded less sensitively to changes in extracellular potassium concentration.

Herpes zoster ophthalmicus and granulomatous angiitis. An ill-appreciated cause of stroke

The syndrome of granulomatous angiitis related to varicella zoster virus infection often manifests as herpes zoster ophthalmicus followed by contralateral hemiplegia. Forty-five cases have been reported to date, and the authors' experience with two additional cases seen in a one-year period is described. Given the frequency of both stroke and herpes zoster ophthalmicus in an aging population, the authors postulate that granulomatous angiitis is underdiagnosed. There is need for increased awareness of this disease by the non-neurologist. Diagnostic and therapeutic considerations are reviewed.

Immunologic modulation by vitamin C in the elderly

Aging is associated with a decline in both humoral-mediated and cellular-mediated immunity. These aberrations may contribute to morbidity and mortality in the elderly. Since we have previously shown that vitamin C enhances in vitro and in vivo immune functions in young healthy volunteers, we studied the effects of vitamin C on certain immunologic parameters in an elderly population. In vitro lymphocyte proliferation to the mitogen concanavalin-A was significantly less when compared to a young control group. When lymphocytes from the elderly were pre-incubated overnight and cultured in the presence of 10 micrograms/ml of vitamin C, mitogen-stimulated lymphocyte proliferation was similar to that from controls without vitamin C in culture. Having demonstrated significant in vitro immunoenhancement with vitamin C, we next studied the effects of oral ingestion of 2 g of vitamin C daily on certain in vitro and in vivo immunologic parameters in the elderly. When compared with a placebo-treated group, 3 weeks of vitamin C treatment did not effect in vitro mitogen-stimulated lymphocyte proliferation or in vivo reactivity to common skin test antigens. The augmenting effects of in vitro vitamin C suggest that this essential vitamin may be an effective agent in modulating aberrant immunologic functions in the elderly. The clinical significance of these findings requires further study.

Age-related changes in lymphocyte subset proportions, surface differentiation antigen density and plasma membrane fluidity: application of the eurage senieur protocol admission criteria

Peripheral blood lymphocytes from 260 "apparently healthy" males and females, aged 20-97, have been investigated for age-related changes in a number of immunological parameters (percent and number of lymphocytes, OKT 4+ and OKT 8+ cells; OKT 4/8 ratio; intensity of fluorescence of OKT 4 and OKT 8 stained cells; membrane fluidity). Data were then reassessed after exclusion of people who did not conform to the SENIEUR PROTOCOL admission criteria of EURAGE (European Economic Community's Concerted Action Program on Aging) in order to investigate whether the differences observed were attributable to underlying disease. A slight decrease in the number and percentage of lymphocytes, OKT 4+ and especially OKT 8+ cells was found. Intensity of fluorescence of OKT 4 and OKT 8 stained cells from the elderly was reduced and may explain the lower percentages. Membrane fluidity was decreased in old persons (over the age of 75); the free cholesterol/phospholipid molar ratio in the serum increased up to the age of 75 and then declined, and it did not correlate with decreased membrane fluidity. Exclusion of the 20-60% of the study groups who were not eligible for admission according to the SENIEUR PROTOCOL criteria did not affect these results. The feasability and applicability of the PROTOCOL is discussed.

Immunosenescence. Clinical and pharmacologic considerations

The effect of aging on the immune response is highly variable. Many individuals appear to maintain adequate immunologic function throughout life, whereas others have severely depressed immunologic responses accounting for disease activity. Both cellular- and humoral-mediated responses may be abnormal in the elderly. Aberrant function of immunoregulatory cells, effector T cells, and antibody-producing B cells contribute to poor immunity in the aged. Immunoenhancement in the elderly by pharmacologic agents appears promising. Several agents have been demonstrated to improve immune responses when administered to aging animals and humans. Although these studies are encouraging, it is not known if enhancement of immune responses in the elderly will be associated with clinical benefits. This issue must still be examined.

Analysis of T regulator cell surface markers and functional properties in multiple sclerosis

The relative proportions as well as cell surface and functional properties of T suppressor (T8+) and T helper (T4+) cells in peripheral blood mononuclear cells ( MNCs ) of MS patients were analyzed. The proportion of T8 cells compared to normal controls was suggestively lower in patients during relapses and significantly lower in those with progressive disease. The density of T8+ antigen on cells of MS patients with active disease as measured by median fluorescence intensity ( MFI ) was also decreased compared to controls and stable MS patients. Using OKT8-mAb modulated MNCs as a model, we found that reduction of T8 antigen density results in substantial discrepancies between FACS and microscope methods for enumeration of T8+ cells. Levels of pokeweed mitogen-induced IgG secretion by MNCs of MS patients did not correlate with proportion of T8+ cells within the MNCs , but rather with the functional activity of the T8+ cells of given individuals, as tested in an in vitro suppressor assay using constant numbers of T8+ cells.