Maximal T cell IL-13 production requires monocyte or monokine participation

The T cell-secreted lymphokine interleukin 13 (IL-13) exerts pleiotropic ef fects on monocytes (M phi) and B cells. Since accessory cells, like M phi a nd B cells, also act in antigen-presenting and lymphokine augmentation of T cells, M phi and B cells may be able to effect T cell IL-13 production. Pu rified T cells produced slightly less IL-13 than the lower T cell numbers c ontained in peripheral blood mononuclear cell population, further suggestin g accessory cell augmentation. Addition of 10% B cells [either unstimulated or pokeweed mitogen (PWM)-stimulated] to autologous T cells only moderatel y augmented T cell IL-13 levels, PWM-stimulated B cell culture supernates h ad even less augmenting effect on T cell IL-13 levels and unstimulated B ce ll culture supernates did not augment T cell IL-13 production. In contrast to the moderately augmenting effect of B cells or their stimulated culture supernates, addition of 10% M phi, either unstimulated or muramyl dipeptide (MDP)+ IFN-gamma stimulated, to autologous T cells produced a highly signi ficant increase in T cell IL-13 production, M phi culture supernates were e qually effective in augmenting T cell IL-13 levels, suggesting both that ce ll-to-cell contact is not critical for M phi augmentation of T cell IL-13 l evels, and that M phi secreted factors are pivotal. CD64(+) M phi (or their culture supernates), which are known as poor antigen-presenting cells, als o effectively augmented T cell IL-13 production, further supporting the inv olvement of M phi secreted factors, Finally, experiments with exogenous add ition of recombinant monokines, as well as neutralization experiments with different cytokine antibodies, suggested IL-1 beta as a primary cytokine in volved in the augmentation of T cell IL-13 levels by accessory cells. Howev er, these experiments also indicated other unidentified M phi factors as pl aying a significant role in producing maximal T cell IL-13 production. (C) 1998 Academic Press.