Immunology
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Immune activities of newly developed, short-lived SAM-P/1 mice declined sharply after a few months of age. As early as 2 months of age, the activity of T-helper (Th) cells ('Th2'-like) in the in vitro primary antibody response was profoundly impaired, in contrast to normal activity of Th cells ('Th1'-like) engaged in cell-mediated immune responses. Thus, young SAM-P/1 mice show a functional heterogeneity of Th cells. ⋯ Further linkage analyses suggest that one of the genes is closely linked to albino coat-colour (c) locus on chromosome 7. The putative two genes are likely to control 'differentiation' or 'maturation' of Th2-like cells defectively, but the defect is not refractory, because in vivo-primed Th cells function in vitro as do those in ordinary strains of mice. Possible mechanisms and biological significance in relation to loss of immune activity with ageing are discussed.