Abstract
Among the eight inbred mouse strains employed in our preceding report, 12-O-tetradecanoylphorbol 13-acetate (TPA) painting alone induced CD4+ regulatory T (Tr) cells in four strains (e.g., C3H/He) at 6—8 weeks of age, but not in the remaining strains (e.g., C57BL/6, BALB/c). In the present study, the effect of growth from 4—14 weeks on delayed-type hypersensitivity (DTH) response was investigated in three inbred murine strains, C3H/He (H-2k), C57BL/6 (H-2b) and BALB/c (H-2d) mice. In all strains older than 10 weeks, DTH response was suppressed exclusively by TPA painting. The defect of suppressive activity for DTH in several of the strains at 6—8 weeks of age was dependent on the presence of cells, which blocked regulatory cell activity at 6—8 weeks of age, but not at 10 weeks of age. The age-dependent difference in regulatory activity was caused by the presence of CD8+ contra-regulatory T (Tcr) cells. CD8+ contra-regulatory T cells are required to contact regulatory cells in order to block DTH suppressive activity. Adhesion molecules were of great importance in contra-suppression, as antibody treatment to LFA-1 or ICAM-1 blocked this activity. ICAM-1 expression on CD4 T cells greatly increased following growth in 10 week-BALB/c mice receiving TPA than 6-week-old mice, however, a slight increase in growth occurred in 6-to-10-week-old animals in which TPA was absent. The degree of increment in body weight was very similar in these inbred strains. Thymus involution in C3H/He mice was the earliest signal among these mice. This result may suggest that the period of differentiation and maturation of T cells in a first lymphoid tissue for the growth process differs in these three inbred strains. This study provides an interesting example of genetic control of maturation or proliferation of peripheral T cells.
