Differential abilities of Th1 and Th2 to induce polyclonal B cell proliferation

Human gamma globulin-specific T helper cell (Th) clones, activated by HGG in the presence of antigen (Ag)-presenting cells, stimulated polyclonal B cell proliferation. Both Th1 and Th2 clones induced B cell proliferation, but Th1 clones were generally 5- to 10-fold less efficient than Th2 in this capacity. Th1 and Th2 each induced proliferation of both small and large B cells, although Th1 induced less B cell proliferation than Th2, regardless of B cell size. Th1-induced B cell proliferation was increased significantly by stimulating the Th1 clones with immobilized anti-CD3 mAb. The B cell response to Ag-activated Th1 clones was also increased by the addition of rIL-4 or culture supernatants from activated Th2 clones, and this enhancement was abolished by addition of anti-IL-4 mAb. The differential capacity of the Th subsets to stimulate B cells could not be attributed to differences in the degree of Ag-induced activation of the Th clones as reflected by Th proliferation or Th expression of activation markers, RL388 Ag, IL-2R, or TfR. Taken together the results suggest that even though Th1 and Th2 are similarly activated by Ag-presenting cells, Ag-activated Th2 interact more effectively with B cells than Ag-activated Th1. It is possible that inefficient interaction and subsequent intercellular signaling between Th1 and B cells results in inefficient Th1-induced B cell proliferation, and that this deficiency may be circumvented by signals (e.g., lymphokines) provided by Th2, or by the stimulation of Th1 with plate-bound anti-CD3 Ab rather than Ag.