Human B cells accumulate immunoglobulin V gene somatic mutations in a cell contact-dependent manner in cultures supported by activated T cells but not in cultures supported by CD40 ligand.
The acquisition of somatic mutations in the rearranged immunoglobulin V regions in B cells occurs within the tightly regulated microenvironment of a germinal centre. The precise mechanism responsible for turning on the mutational process is unknown. To dissect the role of different components of the germinal centre in this mechanism, we have used in vitro cultures of normal human IgD+ peripheral blood B lymphocytes co-cultured with activated CD4+ T cells, or with resting CD4+ T cells, or with CD40 ligand and IL-4. We observed that if the cultures included activated CD4+ T cells, then up to 100% of VH transcripts on day 14 were somatically mutated. Transcripts were found to carry from one to 36 substitutions (median five). In contrast, in the absence of activated T cells, transcripts contained only background levels of somatic mutation irrespective of the presence of resting T cells or CD40 ligand and IL-4. Cell-cell contact was required for mutation because mutations were not detected when B cells were separated from activated T cells by a membrane.
Huang
S C
SC
Virginia Mason Research Center; Department of Immunology, University of Washington, Seattle, WA, USA.
Glas
A M
AM
Pinchuk
G V
GV
Van Montfort
E H
EH
Rao
S P
SP
Jiang
R
R
Milner
E C
EC
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D023201:CD40 Ligand; D002448:Cell Adhesion; D002460:Cell Line; D004247:DNA / Q000235:genetics; D015322:Gene Rearrangement, B-Lymphocyte; D005803:Genes, Immunoglobulin; D006801:Humans; D007074:Immunoglobulin G / Q000235:genetics; D007075:Immunoglobulin M / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D009154:Mutation
D007074:Immunoglobulin G; D007075:Immunoglobulin M; D007135:Immunoglobulin Variable Region; D008562:Membrane Glycoproteins; D023201:CD40 Ligand; D004247:DNA