A. Mori et al., EPITOPE SPECIFICITY OF BEE VENOM PHOSPHOLIPASE-A(2)-SPECIFIC SUPPRESSOR T-CELLS WHICH PRODUCE ANTIGEN-BINDING GLYCOSYLATION INHIBITING FACTOR, International immunology, 5(8), 1993, pp. 833-842
From the spleen cells of BALB/c mice primed with bee venom phospholipa
se A2 (PLA2), we established seven T cell hybridomas which constitutiv
ely secreted glycosylation inhibiting factor (GIF), expressed both CD3
and TCRalphabeta, and responded to antigen-pulsed antigen presenting
cells (APC) for the formation of IgE-binding factor. Upon stimulation
with antigen-pulsed APC, four of the seven hybridomas produced GIF hav
ing affinity for native PLA2. The antigen-binding GIF could suppress t
he anti-hapten antibody response of BALB/c mice to dinitrophenyl (DNP)
- PLA2 conjugates in a carrier-specific manner and bound to immunosor
bents coupled with either the mAb 14-12 or anti-TCRalpha chain, H28-71
0. Analysis of the epitope specificity of the TCR on the GIF-producing
T hybridomas indicated that all of the hybridomas which could produce
antigen-binding GIF upon antigenic stimulation recognized the synthet
ic peptide representing amino acid residues 19 - 34 in PLA2 molecules
in the context of the product of the I-A(d) subregion and the antigen-
binding GIF formed by the cells had affinity for the peptide. The 3-D
structure of bee venom PLA2 indicates that the sequence of amino acid
14 - 24 forms a loop in the PLA2 molecule and represents an external s
tructure of the antigen, while peptide 25 - 37 forms an alpha helix. E
vidence was obtained which suggests that the sequence of 25 - 34 conta
ins amino acid residues interacting with la molecules, while peptide 1
9 - 24 contains residues involved in the interaction of p19 - 34 - la
complexes with TCR on the hybridomas. It was also found that not only
the synthetic peptide 19 - 34, but also the peptides 13 - 28 and 19 -
30 inhibited the binding of antigen-binding GIF to PLA2-coupled Sephar
ose, while peptide 25 - 40 failed to do so. The results collectively i
ndicate that the antigen-binding GIF and TCR on the cell source of the
factor interact with a common epitope which is exposed on the surface
of a nominal antigen.