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In the previous paper we showed that the immune response to sheep red cells (SRBC) was degenerate; serum antibodies showed increasing loss of specificity, signalled by cross-reactions with horse RBC (HRBC), with time after immunization and with hyperimmunization. In the present report we have analysed the role T cells may play in this process. To do this we studied the antibodies made by mice deprived of T cells by irradiation as well as those made by normal mice immunized with SRBC in distilled water, which was shown to depress the DNA synthetic response of T cells. In both instances the mice with fewer responding T cells made less antibody which could agglutinate HRBC than did the appropriate controls. This was true even when no difference in anti-SRBC titre was apparent. In addition we showed that the antibody made by mice with reduced numbers of T cells was less effective at passive suppression of the immune response to SRBC than was similarly titred (against SRBC) antibody made by normal mice. Thus, certain sub-populations of antibodies, normally made in response to SRBC, immunization, are particularly thymus dependent. We have discussed why we think they are those of particularly high affinity. [ABSTRACT FROM AUTHOR]

The effect of an horse anti-mouse thymocyte globulin (ALG) preparation on the primary and secondary immune responses to sheep erythrocytes (RBC) was studied in 2-3-month-old male A/HeJ, C57B1, BALB/c, DBA/1, CBA and C3H mice. A wide variation in the primary and secondary responses of the individual strains was noticed but in ail cases these were significantly suppressed by ALG pretreatment. The capacity of the ALG to suppress the primary immune response was not overcome by increasing the antigen dose from 3 × 107 to 3 × 109 sheep RBC. [ABSTRACT FROM AUTHOR]

Long-term IgM and IgG responses to sheep red blood cells (SRBC) were determined in New Zealand Black (NZB) mice, using the plaque technique. As compared with other strains a prolonged spleen plaque-forming cell (PFC) response was found in young and old NZB mice. This phenomenon was found in the primary as well as in the secondary response and concerned IgM as well as IgG production. These observations are discussed in relation to the production of IgG antibodies of a low avidity. [ABSTRACT FROM AUTHOR]

A time-course study of total, 19S and 7S haemolysins showed that Swiss albino mice were able to give a normal secondary response to sheep erythrocytes at an age when the primary response was much reduced and delayed.

India ink or other finely divided agents (trypan blue, saccharated iron oxide, thorotrast, polystyrene latex) were injected intravenously into mice, and sheep erythrocyte stroma injected subsequently by the same route. The splenic uptake of stroma carrying a tag of 131I was consistently higher in mice treated with the 'blockading' agents than in untreated controls, the difference in some experiments being greater than ten-fold. In addition to promoting the splenic uptake of antigen, some of the finely divided agents also enhanced the formation of anti-sheep red cell haemolysin in mice immunized with a single intravenous injection of sheep erythrocyte stroma. India ink injected intravenously caused a significant rise in the splenic weight of mice. [ABSTRACT FROM AUTHOR]

The organ distribution, blood clearance rate, and immune response to intravenous 51Cr-labelled sheep red blood cells (SRBC) have been studied in mice, following administration of a single intravenous dose of colloidal carbon. In normal mice 80-90 per cent of SRBC were found in the liver and 2-6 per cent in the spleen. The blood clearance rate of SRBC was extremely rapid. Colloidal carbon caused a marked depression of hepatic uptake of SRBC and a corresponding increase in splenic uptake. This effect was maximal at 6 hours after carbon administration and recovery of hepatic phagocytosis occurred over 4 days. The rate of clearance of SRBC was greatly reduced while the hepatic uptake of red cells was depressed. At low doses of cells there was an increase in titre of humoral antibody and in numbers of spleen PFCs while, at high doses of cells, a slight depression in immune response occurred. 'Stimulation' of splenic uptake of antigen and of the immune response by colloidal carbon is associated with depression of hepatic phagocytosis. [ABSTRACT FROM AUTHOR]