title: Antigen presentation is a function of all B cell subpopulations separated on the basis of size.
abstract: Purified splenic B cells from nonimmune mice were separated by counterflow centrifugal elutriation into 6 subpopulations containing cells of discrete sizes ranging from 119 to 200 micron3. B cells of each subpopulation were competent to process and present a native globular protein antigen, cytochrome c, to a cytochrome c-specific T cell hybrid. In all cases, the B cells' antigen-presenting function was radiation sensitive and did not require T cells or T cell products, since B cells fixed with paraformaldehyde effectively presented a carboxyl-terminal peptide fragment of cytochrome c containing the T cell determinant. Furthermore, the antigen-presenting function of B cells of each subpopulation was augmented by treatment with submitogenic doses of the F(ab')2 fragment of rabbit anti-mouse Ig antibodies, in that 10-30-fold fewer B cells were required and higher maximal T cell responses were achieved, indicating that B cells of all sizes are capable of being regulated in their antigen presentation function through their surface Ig. In addition, B cells of each subpopulation responded to soluble factors present in the supernatants of activated T cells as evidenced by an increase in volume and by the uptake of [3H]thymidine. These results indicate that B cells, regardless of size, are able to participate in at least two essential phases of T cell-dependent antibody responses, initiating the interaction by processing and presenting antigen to helper T cells and responding to soluble helper factors secreted by activated T cells.
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000187:drug effects / Q000276:immunology* / Q000528:radiation effects; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology*; D002454:Cell Differentiation; D002469:Cell Separation; D002999:Clone Cells; D003574:Cytochrome c Group / Q000276:immunology; D005557:Formaldehyde / Q000494:pharmacology; D006133:Growth Substances / Q000494:pharmacology; D015847:Interleukin-4; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation / Q000528:radiation effects; D008222:Lymphokines / Q000494:pharmacology; D051379:Mice; D011108:Polymers / Q000494:pharmacology; D011947:Receptors, Antigen, B-Cell / Q000276:immunology; D013154:Spleen / Q000166:cytology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D003574:Cytochrome c Group; D006133:Growth Substances; D008222:Lymphokines; D011108:Polymers; D011947:Receptors, Antigen, B-Cell; D005557:Formaldehyde; D015847:Interleukin-4; C003043:paraform