TACI deficiency decreases production of ASCs in a B cell–autonomous manner. (A-B) The number of ASCs was restored by adoptive transfer of TACI-wt B cells but not by transfer of TACI-wt T cells into TACI-deficient recipients. NP-specific IgM (A) or NP-specific IgG (B) ASCs were enumerated by ELISPOT of splenocytes 14 days after immunization, and after reconstitution by adoptive transfer of QM-TACI-wt or QM-TACI-ko B cells, and C57BL/6-wt or C57BL/6-TACI-ko T cells. Representative pictures of the ELISPOT wells are shown below each graph. Transfer efficiency was equivalent in all experiments and determined by enumerating IgM^a-positive donor B cells by FACS analysis in the spleen of recipients at the time of analysis. The number of IgM-secreting cells was significantly decreased whenever reconstitution was done with TACI-ko B cells: *P = .016 (2-way ANOVA). The number of IgG-secreting cells in animals reconstituted with TACI-ko B cells and TACI-wt T cells was significantly decreased compared with animals reconstituted with TACI-wt B and T cells: *P = .041 (t test). Data resulted from analysis of 3 recipient mice for each type of transfer.