THYMUS-INDEPENDENT B-CELL ACTIVATION - PASSIVELY INCORPORATED MEMBRANE ANTIBODIES SERVE TO FOCUS THE ANTIGEN BUT CANNOT TRANSMIT ACTIVATION SIGNALS

We have activated B cells with membrane‐incorporated monoclonal antibodies against the hapten trinitrophenyl (TNP) using various concentrations of the polyclonal activator lipopolysaccharide (LPS) haptenated with TNP, We found that anti‐TNP‐decorated B cells were polyclonally activated by 1000‐fold lower concentrations of TNP LPS than untreated B cells or B cells decorated with antibodies of other specificities. In order to test whether the passively incorporated anti‐TNP monoclonals could mediate activation signals or only served to focus the polyclonal activator TNP‐LPS to the B cells, we compared the response of anti‐TNP‐decorated B cells from normal C3H/He mice and from the LPS‐unresponsive strain C3H/HeJ. We found that B cells from C3H/HeJ mice could not be activated to polyclonal antibody synthesis, in contrast to B cells from the LPS‐responsive strain C3H/He. Thus, contrary to what was previously suggested [9], the incorporated anti‐TNP antibodies could not mediate activation signals, but only served to passively bind and concentrate TNP‐LPS to the membrane of the B cells, thereby increasing the concentration of the polyclonal B‐cell activator LPS to the B cells. Copyright © 1990, Wiley Blackwell. All rights reserved