The γδT cell receptor(TCR) is expressed on a distinct subset of T lymphocytes. Unlike the αβTCR bearing T lymphocytes(αβ T lymphocytes), nearly allγδTCR bearing T lymphocytes(γδT lymphocytes) lack expression of CD4 and CD8. Accordingly,
these
CD3+CD4-CD8-γδT lymphocytes are not restricted by MHC class I or MHC Ⅱmolecules, and it seems that γδT lymphocytes may use other presenting molecules for antigen recognition. However, what kind(S) of molecule(S) are involved in the specific
antigen
recognition of γδT lymphocytes still remains to be elucidated.
@EN The CD1 family has homology with MHC class I and the products are very similar to each other in three dimensional structure. Furthermore, CD1 molecules are associated with β2-microglobulin just like MHC class I molecules. Hence are they
called
"MHC
class I-like Molecules" and are regarded as the best candidate for the antigen-presenting molecule ofγδ T lymphocytes. Thus we studied whether and how CD1 in involved in antigen recognition of γδT lymphocytes using antigen-specific model.
@ EN To establish the antigen-specific model , we made human CD3+cd4-CD8-γδT cell clones specific to M. tuberculosis and among them. LC29 was selected to be used to determine whether anti CD1a antibody block the antigen recognition of γδ T
cell
clone.
Anti-CD1a monoclonal antibody, BL6, inhibited the thymidine incorporation, the phosphorylation of CD3ζ chain, and IL-2 and IFN-r secretion of LC29 cells stimulated with mycobacterial sntigen. Taking these results into account, CD1a is certainly
involved in the recogintion of mycobacterial antigen by LC29 clone.
To determine whether CD1a can function as antigen-presenting molecule for γδT lymphocytes, we investigated the affinity of γδT lmphocyte for human CD1a-transfectant L cells, and physical association between CD1a and mycobacterial antigens.
The
results showed that LC29 cells had affinity to L2LA4.4 cells expressing CD1a, and this affinity was blocked by F(ab')2 of OKT6 monoclonal antibody specific to human CD1a. Immunoblot analysis of the CD1a-immunoprecipitates from the extracts of
human
peripheral blood mononuclear cells pretreated with mycobacterial antigens by monoclonal antibody cocktail to M. tuberculosis revealed specific bands. Therefore, it was suggested that CD1a could function as an antigen presenting molecule for γδT
lymphocytes sepcific to M. tuberculosis.
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