Quantitative characteristics of antibody forming cells in partial tolerance.

Direct PFC to SRBC were enumerated simultaneously by the LHL and LHG in the spleens of partially tolerant and control rats. The sensitivity of LHL was higher than that of LHG, but the factor by which the number of PFC was higher in LHL than in LHG was in the two groups similar (1.44 in tolerant and 1.47 in control group). When the plaque size distribution was studied in the LHL, a significant increase in small size plaques was observed in tolerant rats. The findings are discussed and the conclusion is reached that the decrease in AFC number and not in antibody production by individual PFC is the main factor responsible for partial tolerance.