Lipopolysaccharide-stimulated events in B cell activation.
High concentrations of thymus-independent (TI) antigens are capable of inducing polyclonal B cell activation by their intrinsic mitogenic properties, irrespective of the specificity of the Ig receptors. Due to a genetic defect on the 4th chromosome, B cells from C3H/HeJ mice do not respond to lipopolysaccharide (LPS). In order to define at which step the mutation affects the signalling pathway, we compared B cells from C3H/HeJ and CBA mice with regard to changes of three events, namely cell size, and MHC class I and II antigen expression after LPS stimulation. We found that cell size and expression of MHC antigens increase in B cells from CBA mice after LPS stimulation, whereas B cells from C3H/HeJ mice do not respond at all. This suggests that the defect in C3H/HeJ mice interferes with early events in the signalling pathway, either due to the absence of a LPS receptor on B cell surface or the lack of an initial component necessary for effective signal transmission subsequent to LPS receptor binding. Our results also have shown that stimulation of anti-Ig antibodies and LPS differ in some signalling events and have different final effects on B cells, which suggests that they may function differently via distinct signalling pathways.
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Department of Immunology, Arrhenius Laboratories for Natural Sciences, Stockholm University, Sweden.
Möller
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D000818:Animals; D001402:B-Lymphocytes / Q000187:drug effects / Q000502:physiology*; D048429:Cell Size; D002478:Cells, Cultured; D005434:Flow Cytometry; D006462:Hemolytic Plaque Technique; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis; D007075:Immunoglobulin M / Q000502:physiology; D015847:Interleukin-4 / Q000502:physiology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D051379:Mice; D008809:Mice, Inbred C3H; D008808:Mice, Inbred CBA; D013154:Spleen / Q000166:cytology
D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II; D007075:Immunoglobulin M; D008070:Lipopolysaccharides; D015847:Interleukin-4