SOME IMMUNOLOGICAL PARAMETERS AS INDICES OF AGING IN NIGERIANS

Abstract

This study involved 541 participants. It assessed the state of body defence mechanisms during ageing in 217 healthy Nigerians aged 6-95 years. A different group of 274 healthy subjects of ages 6 to 60 years were studied for mantoux test responses. In vitro cell-mediated immune response was analyzed by the Leucocyte migration inhibitory factor (L- MIF) test using concanavalin A, candida antigen, measles and BCG vaccines. Numerical estimates of B-lymphocytes, T-lymphocytes, helper T-cells and suppressor T-cells were determined by immunofluorescence assay. Percentage null cell was derived by difference between 100 and the sum of pan T cell and B cell. Also examined were specific humoral immune factors including the immunoglobulins(IgG, IgA, IgM, IgD) and the determination of isohaemagglutinins. Antibody response to meningococcal polysaccharide vaccination was examined in another group of 50 subjects aged 18-55 years. Non-specific cellular immune capacity was studied by the nitroblue tetrazolium (NBT) test and total and differential leucocyte counting. Non-specific humoral immune factors studied include complement components and acute phase proteins (transferrin, albumin, C-reactive protein, alpha 2 macroglobulin), Miscellaneous immunologic indices were also analyzed. These Include the levels of circulating immune complexes (CIC), the prevalence of antinuclear antibodies (ANA) and rheumatoid factors (RF). Mean L-MIF activity decreased with rising age. The mean tuberculin reaction diameter increased progressively between the ages of 6 and 40 years, and began to decrease in subjects whose ages were above 50 years. The numbers of B-cells, T-cells, null cells, helper T-cells, and suppressor T-cells were the same in the different age groups. T-cell subpopulation did not correlate (P>0.02 ) with migration inhibition. Of the humoral factors, only C4. CIC and the prevalence of ANA and RF show significant alteration (increasing values) with age. The results indicate a progressive decline in cellular immune function with age. The possibility that CIC and auto-antibodies may be useful in indexing ageing, especially in community studies, exists.