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, 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.
Department of Immunology, University of Stockholm, Sweden.
M
M
Alarcón-Riquelme
G
G
Möller
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D008070:Lipopolysaccharides / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D008809:Mice, Inbred C3H; D011947:Receptors, Antigen, B-Cell / Q000502:physiology*; D013950:Thymus Gland / Q000502:physiology*; D014301:Trinitrobenzenes / Q000276:immunology; D005719:gamma-Globulins / Q000276:immunology
D008070:Lipopolysaccharides; D011947:Receptors, Antigen, B-Cell; D014301:Trinitrobenzenes; D005719:gamma-Globulins