Epitope of MHC class I mAb W6/32

John Ladasky ladasky at leland.Stanford.EDU
Wed Dec 4 20:26:17 EST 1996

In article <E1wBst.BMq at fsa.bris.ac.uk>,
S.D. Wainwright <ogsdw at ssa.bris.ac.uk> wrote:
>Can someone point me at refernces which describe
>the epitope of the human class I mAb W6/32
>Thanks in advance
>Shane Wainwright

	The W6/32 antibody reacts with all human class I molecules when
associated with beta-2 microglobulin.  W6/32 also reacts with class I
molecules from several other mammalian species.  The heavy-chain component
of the W6/32 epitope was mapped by comparing the sequences of various
reactive and non-reactive heavy chains.  The conclusion is that residue
121 of the heavy chain must be a lysine in order for W6/32 to bind.

	The association of the heavy chain with b2m is necessary but not
sufficient for the formation of the W6/32 epitope.  Even after many rounds
of immunoprecipitation with W6/32, other pan-HLA antibodies can pull down
lots of b2m-associated HLA-A, B, and C molecules.

	In a manner analogous to the heavy-chain sequence comparisons,
b2m sequences from various species have been compared in order to map the
b2m portion of the W6/32 epitope.  Now I hope you will excuse me while I
don my editorial hat and state that I think that the published b2m data
is incorrect.  Based on the sequences available in the late 1980's, re-
searchers concluded that residues 45 and 89 of the b2m molecule comprised
the b2m determinant of W6/32.  These residues are a long way from the 
residue in the heavy chain, over 25 angstroms as I recall.  The two resi-
dues aren't even that close to each other.  The argument has been advanced
that W6/32 recognizes a "large, discontinuous, conformational epitope" on
class I molecules.

	The problem, in my opinion, is that the sequences then available
had distracting, extraneous polymorphisms, and that there weren't enough 
sequences with the informative polymoprhisms.  In a few weeks, I hope to
submit a manuscript in which I derive a simpler picture from some new b2m
sequences.  I'm just waiting for one last transfectant to grow!

	Here's my list of references.  Good luck.


Barnstable, C. J., W. F. Bodmer, et al. (1978). *Production of Monoclonal
Antibodies to Group A Erythrocytes, HLA, and Other Human Cell Surface
Antigens - New Tools for Genetic Analysis.* Cell 14: 9-20.

Brodsky, F. M. and P. Parham (1982). *Evolution of HLA Antigenic
Determinants: Species Cross-reactions of Monoclonal Antibodies.*
Immunogenetics 15: 151-166.

Crepaldi, T., S. D'Alfonso, et al. (1991). *Activated human T cells express
b2-microglobulin-associated HLA-A,B,C molecules not recognized by W6/32 mAb.
Tissue Antigens 37: 138-140.
Jefferies, W. A. and G. G. MacPherson (1987). *Expression of the W6/32 HLA
epitope by cells of rat, mouse, human and other species: critical dependence
on the interaction of specific MHC heavy chains with human or bovine b2-
microglobulin.* Eur. J. Immunol. 17: 1257-1263.
Kahn-Perles, B., C. Boyer, et al. (1987). *Acquisition of HLA Class I W6/32
Defined Antigenic Determinant by Heavy Chains from Different Species
Following Association with Bovine b2-microglobulin.* J. Immunology 138(7):
Maziarz, R. T., J. Fraser, et al. (1986). *The human HLA-specific monoclonal
antibody W6/32 recognizes a discontinuous epitope within the alpha 2 domain
of murine H-2Db.* Immunogenetics 24(3): 206-208.
Parham, P. and H. L. Ploegh (1980). *Molecular Characterization of HLA-A,B
Homologues in Owl Monkeys and Other Nonhuman Primates.* Immunogenetics 11:

Parham, P., P. K. Sehgal, et al. (1979). *Anti HLA-A,B,C monoclonal
antibodies with no alloantigenic specificity in humans define polymorphisms
in other species.* Nature 379: 639-641.

Unique ID : Ladasky, John Joseph Jr.
Title     : BA Biochemistry, U.C. Berkeley, 1989  (Ph.D. perhaps 1998???)
Location  : Stanford University, Dept. of Structural Biology, Fairchild D-105
Keywords  : immunology, music, running, Green

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