mAb and CR2Fc treatment does not increase overall survival in C6-deficient mice. Survival of C6-deficient mice challenged with EL4 and treated with 14G2a alone or in combination with CR2Fc. mAb therapy with or without CR2Fc did not provide long-term protection in the absence of C6, although it did significantly (P < .05) prolong survival time. CR2Fc did not enhance the effect of mAb therapy in C6-deficient mice; n = 4 to 6.