Interleukin 1 induces T cell mediated differentiation of murine Peyer's patch B cells to IgA secretion

Peyer's patches (PP) represent an important source of cells potentially capable of secreting IgA, yet, under normal circumstances, little IgA is produced in the PP. This study has evaluated the regulatory role of cytokines in the differentiation of PP B cells. When recombinant human interleukin 1 alpha (rIL 1) was added to cultured PP cells in a concentration as low as 0.75 U/ml (5 pg/ml protein concentration) IgA secretion was increased four- to six-fold. This action of rIL 1 was T cell dependent, in that rIL 1 did not induce IgA differentiation in PP cultures previously depleted of T cells. The addition of rIL 1 to cultures containing splenic T cells and PP B cells or PP T cells and splenic B cells did not result in IgA secretion. Thus, the in vitro stimulatory action of rIL 1 required that both B cells and T cells be of PP origin. Additionally, when irradiated (3000 R) PP T cells were cultured with PP B cells in the presence of rIL 1, no IgA secretion was observed. The indirect stimulatory effect of IL 1 on PP B cells could not be reproduced when PP B cells were cultured with recombinant preparations of interleukins 2 and 4. These experiments strongly suggest that IL 1 is capable of stimulating IgA production by PP cells in vitro by means of activating an intermediate T cell that, in turn, regulates IgA differentiation in PP B cells.