| Abstract: | Inbred mice of various strains, 3–4 months of age and 16 months or older, were given primary injections of allogeneic spleen cells to observe the time of appearance and relative levels of alloantibodies of IgG1 and IgG2 class. In 3–4 month old C3H mice injected with BALB/c spleen cells, IgG2 alloantibodies were present on day 6, before the appearance of alloantibodies of IgG1 class. The IgG2 class alloantibodies then continued to increase in level until day 12. IgG1 class antibodies, which appeared after day 6, also increased during this period. When C3H mice at 16 months of age were similarly injected a difference in response was found in that IgG2 class alloantibodies did not increase in level after the appearance of those of the IgG1 class, but IgG1 class alloantibodies increased until day 12, as in the young mice. At intermediate ages smaller effects in the same directions were observed. Young BALB/c mice injected with C3H spleen cells gave responses similar to those of the young C3H mice. At 16 months, however, the response was not different from that of the young BALB/c mice. At older ages (19–25 months) the response of BALB/c mice was similar to that of the 16-month-old C3H mice described above. CBA mice of various ages which were injected with BALB/c spleen cells showed effects similar to that of the BALB/c mice in that a change of response seen in the older CBA mice, similar to that of the other two strains, did not appear at 16 months of age but did appear later (20–24 months). |
