QUANTITATIVE ANALYSIS OF CHIMAERIC STATE IN MICE .2. CYTOLOGICAL EXAMINATION OF PROPORTION OF PROLIFERATING DONOR AND HOST CELLS IN RUNT DISEASE IN MICE

Abstract

The distribution of donor cells in thelymphoid organs of mice suffering from acute runt disease was investigated by means of the cytological marker (T6). In all the strain combinations studied relatively low proportions of donor cells were identified in the spleen and bone marrow. In the A[forward arrow]CBA-T6T6 and C57B[forward arrow] CBA-T6T6 combinations high proportions of donor cells were found in the lymph nodes and thymus. Few donor cells at all lymphoid sites were identified in the CBA-T6T6[forward arrow]C57BL combination, though the recipients showed unquestionable clinico-pathological signs of runt disease. Despite marked splenomegaly in 12-day-old runts, the mean total number of cells in the spleen was similar to that in normal mice and mice injected at birth with isologous cells. In the A[forward arrow]CBA-T6T6 and C57BL[forward arrow]CBA-T6T6 combinations donor cells significantly contributed to the total cellularity of the enlarged spleen, in contrast to the CBA-T6T6[forward arrow]C57BL combination in which the host''s spleen consisted almost exclusively of host cells. Grafting tests showed that runted mice can be either non-specifically or specifically tolerant which seemed to depend on the degree of lymphoid atrophy and the degree of chimerism. Some of the animals that eventually rejected skin grafts from spleen inoculum donors, continued to be chimeric for donor lymphoid cells. A mechanism for runt disease could be mutual interaction between donor and host cell populations causing reduction of the host''s lymphoid reserve and consequent appearance of clinical symptoms of disease.