[Antigen presentation of human B lymphocytes on BCG particulate antigen]

The possibility of human B lymphocytes to process and present BCG particulate antigen to BCG specific T cell line was studied. It was found that about 6% of B cells after incubated with BCG for 24 h, showed BCG bacilli in their cytoplasm, by acid fast stain, and became obscure 48 h later. These results demonstrated that human B lymphocytes could phagocytose, process, and degrade BCG particulate antigen. The BCG pulsed B cells acted as antigen presenting cells to BCG specific T cell line. The proliferation and IL-2 production of specific T cell line were significantly enhanced by BCG pulsed B cell stimulation. It was evident that BCG antigen was presented to T cell lines by B cell. The activity of BCG pulsed B cell was time depending. By treating B lymphocytes with chloroquine which interferes with normal lysosome functions could completely inhibit the proliferation of BCG specific T cell line when B lymphocytes were pulsed with BCG or express of BCG. The results revealed that B cells must process antigen before presenting antigen to T cells. It is concluded that B lymphocytes can phagocytose, process and present relevant determinants of BCG particulate antigen to BCG specific T cell line, and that human B lymphocytes may play an important role in the anti-tuberculous immunity in vivo, at least as antigen presenting cells. To pursue the study of this problem, it is suggested to use B lymphocytes deficient mice as experimental models for further investigation.