Proliferation of hemolysin-plaque-forming cells in nude mice and normal littermates subjected to antigenic competition.

The increase of PFC per spleen and the development of hemolytic foci were examined to clarify the patterns of clonal expansion of B-lymphocytes in athymic nude mice (nu/nu) and normal littermates (nu/+) subjected to the procedure for antigenic competition between horse erythrocytes (HRBC) and sheep erythrocytes (SRBC). In normal littermates without pretreatment with HRBC, a small number of PFC and hemolytic foci of small size were detected 2-days after the challenge with SRBC. The number of PFC increased progressively from day 2 to day 4, and hemolytic foci increased in the number and size during the period. In nude mice, a small number of PVFC were detected on day 2 and the number increased only slightly from day 2 to day 4. No large hemolytic foci were detected during the period. In normal littermates subjected to the procedure for antigenic competition, the patterns of increase of PFC and development of hemolytic foci were similar to those in nude mice. In nude mice, the procedure for antigenic competition exerted almost no effect on the patterns.