Uptake of 51Cr-SRBC in low- and high-responder mouse strains.

We have studied 51Cr-SRBC antigen clearance in two strains of mice differing in the capacity to react with IgG antibody formation. In the B10 strain which is a poor IgG anti SRBC producer, before immunization 80.3% of the injected radioactivity is taken up by liver, whereas after primary stimulation only 31.1%. This value decreases further to 22.8% after secondary stimulation. The well IgG antibody producing A/J strain accumulates in liver before immunization less antigen than the poorly responding strain (69.8%). On the 10th day after primary immunization there is a higher uptake of the radioactivity in liver than in the poor responder strain (53.8%) and this difference is even more pronounced after the secondary stimulation (49.6%). Interaction between peritoneal macrophages of the B10 and A/J strains before and after immunization with SRBC antigen was assessed from the formation of rosettes. Before immunization the low-responder strain B10 exhibited a three times higher level of rosette-forming macrophages, i.e. 6.1% than the high-responder strain A/J (2.0%). However, after immunization the RFM level in the A/J strain increased sevenfold (13.5%) whereas that in the low-responder strain B10 remained unaffected. These results suggested a role of macrophage population in regulation of IgG antibody response.