Specific antibody responses could be induced in serumfree condition. Specific anti-SRBC or anti-SRBC ghost antibody were induced from anti-Thy treated (T-depleted) murine spleen cells in serum-free culture in the presence of Con A conditioned medium. This induction system may facilitate the study of lymphokine functions on antigen triggered B cells. In T cell-replaced cultures, the antibody responses of B cells could be successfully induced when soluble SRBC membrane proteins were used as antigens. It thus indicates that antigen together with lymphokines are sufficient to drive B cells to become antibody secreting cells in the absence of T cells. The T cell-replaced system provides a more stable way for in vitro immunization and may be applied to monoclonal antibody production when in vivo immunization is difficult to be carried out. Specific anti-SRBC or anti-SRBC ghost antibodies were induced from anti-Thy treated (T-depleted) murine spleen cells in serum-free culture in the presence of Con A conditioned medium. This In T cell-replaced cultures, the antibody responses of B cells could be successfully induced when soluble SRBC membrane proteins were used as antigens. It thereby that antigen together with lymphokines are sufficient to drive B cells to become antibody secreting cells in the absence of T cells. The T cell-replaced system provides a more stable way for in vitro immunization and may be applied to monoclonal antibody production when in vivo immunization is difficult to be carried out.