IgG response in vitro. I. The requirement for an intermediate responsive cell type.

We have studied a secondary IgG anti-dinitrophenyl response in dissociated mouse spleen cell cultures which is comparable in magnitude to the responses detected after adoptive transfer. The data indicate that the responsive precursor cell is not a recirculating memory cell but is an intermediate B cell type which appears in vivo after antigen challenge of primed mice. Both antigen and T helper cells are required for in vitro stimulation of the intermediate cell type into the division and maturation steps leading to IgG antibody secretion. The buoyant density of precursor cells has been analyzed by bovine serum albumin density gradient centrifugation, and is consistent with their recent origin by division from memory cells.