In this study Wt FDCs were co-cultured with Wt OVA-specific lymphocytes or with FcgRIIB KO lymphocytes in the presence of IC with or without C’(see bar graph and key above). The depressed Ab response typical for old FDCs is avoided when using KO lymphocytes because the cross linking of BCR and B cell Fc that would inhibit B cells can’t take place when FDCs loose FcgRIIB with aging. Addition of C’ also improves the Ab respnse by providing more CD21L for costimulation. In young FDCs the numerous FcR prevents IC-Fc from cross linking BCR and B cell FcgRIIB and thus prevent B cell inhibition.