Figure 3.

The IgG responses to RNase are CD4⁺ T cell dependent, and the differential immunogenicity between RNase-A and RNase-S is independent of the mouse strain and the route of injection. CD4^−/− and MHC class II^−/− mice on the C57BL/6 background (A) and mice from the C3H/HeJ and B6D2F1 strains (B) were immunized by intraperitoneal injection of a mixture of RNase-A and FITC–RNase-A or RNase-S and FITC–RNase-S (1 μg each) adsorbed onto Alum twice at a 2-wk interval. 10 d after the last injection, the sera were collected, and IgG anti-RNase and anti-FITC were titrated by ELISA. (C) Experiments shown as in A and B, except that C57BL/6 mice were immunized by intradermal or intramuscular injection of antigens. The horizontal lines represent the mean value of each group. N.D., none detected.