Evaluation of immune responses to T-dependent and T-independent antigens. (A) Analysis of anti–sheep red blood cells (SRBCs) antibody response. Tcl1^-/- mice and Tcl^+/+/Tcl^+/-control mice immunized intravenously with SRBCs were bled at day 7 and day 15, and the serum samples analyzed for SRBC-specific IgM and IgG subclasses by ELISA (relative units/mL). Day 7 data only is shown here since antibody levels were similar at both time points. ^*Differences between Tcl1-deficient and wild-type mice were statistically significant (P < .02) by Student t test analysis. (B) Analysis of anti-phosphocholine (PC) antibody responsiveness. Seven 11- to 16-week-old mice in the experimental and control groups were immunized intraperitoneally with 1 × 10⁸S pneumoniae and serum samples obtained one week later were analyzed for PC-specific IgM antibodies by ELISA (relative units/mL). ^*Differences between Tcl1-deficient and wild-type mice were statistically significant (P < .02) by Student t test analysis.