Strain differences in the postnatal development of the mouse splenic lymphoid system.

Four strains of mice, CBA/J, BALB/c, C57BL/6J and B10.BR, were studied for cellular composition of the developing spleen in postnatal life. Considerable strain differences were found in the absolute numbers of splenic lymphoid cells at various ages, the frequencies of B and T cells, the L3T4/Lyt-2 ratio and the time of appearance of IgD and class II antigen on B cells. These observations are discussed in view of strain differences described for the acquisition of immune responsiveness and for susceptibility to tolerance induction in neonates. Finally, it was found that the expression of I-E antigen is delayed compared to that of I-A in ontogeny and possibly during B-cell differentiation as well.