Mechanisms of the failure of resting B cells to present tetanus toxoid antigen to T cells.

The present study examines the failure of resting B cells to present tetanus toxoid (TT) antigen to T cells. A hybrid antibody directed against TT and against human IgM was prepared from immunosorbent-purified rabbit anti-TT and rabbit anti-human IgM. Peripheral blood B cells were prepared by double rosetting with sheep red cells and were depleted of monocytes by double adherence over plastic plates and by passage over a Sephadex G-10 column followed by treatment with OKM1 and complement. B cells were preincubated with medium or with hybrid antibody (60 micrograms/ml) for 1 hr at 4 degrees C, washed, irradiated (2500 R), and tested for their capacity to present TT to an autologous TT-specific T cell clone. B cells coated with the hybrid antibody took up equivalent amounts of 125I-TT as monocytes or EBV-B cells and they internalized fluorescein-labeled TT. In contrast, in the absence of hybrid antibody B cells took up negligible amounts of TT antigen. However, B cells preincubated with the hybrid antibody failed to induce proliferation of autologous TT-specific T cell clones in response to TT. This was not corrected by the addition of partially purified human interleukin I. EBV-B cells sequentially pulsed with hybrid antibody and then with TT for 1 hr at 4 degrees C were equivalent in their capacity to induce T cell proliferation to EBV-B cells presenting soluble TT to the T cells. In contrast EBV-B cells pulsed with TT alone at 4 degrees C failed to take up and present TT. Thus the failure of hybrid antibody-coated resting B cells to present TT reflects an intrinsic inability of the resting B cells to present antigen. Monolayers of hybrid antibody-coated B cells pulsed with TT were prepared on anti-human Fab-coated dishes and were compared with monolayers of TT-pulsed monocytes for their capacity to adsorb TT-specific autologous T cells. In contrast to TT-pulsed monocytes, TT-pulsed hybrid antibody-coated B cells completely failed to bind TT-specific T cells. These results suggest that in addition to their poor antigen uptake resting B cells are incapable of processing antigen and generating the immunogenic moiety recognized by the T cells.