Rarity of autoantibodies to a major autoantigen, thyroid peroxidase, that interact with denatured antigen or with epitopes outside the immunodominantregion
J. Guo et al., Rarity of autoantibodies to a major autoantigen, thyroid peroxidase, that interact with denatured antigen or with epitopes outside the immunodominantregion, CLIN EXP IM, 117(1), 1999, pp. 19-29
The nature of the autoantibody repertoire to the dominant autoantigen in hu
man autoimmune thyroid disease is controversial. There is evidence that aut
oantibodies to thyroid peroxidase (TPO) interact with overlapping conformat
ional epitopes in an immunodominant region and binding to denatured (DN) pr
otein is decreased. Contrary data demonstrate TPO autoantibody reactivity w
ith DN-TPO or polypeptide fragments. However, none of the TPO-specific, hum
an monoclonal autoantibodies isolated to date preferentially recognize dena
tured autoantigen. We therefore searched an immunoglobulin gene phage displ
ay library for human autoantibodies that bind TPO denatured by reduction an
d alkylation (DN-TPO). Thyroid-infiltrating B cells from a typical TPO auto
antibody-positive patient were the source of mRNA for library construction.
Surprisingly, the library enriched after panning on DN-TPO, as well as a p
anel of individual clones, preferentially bound native (N)-TPO. Of 13 clone
s selected using DN-TPO or N-TPO, 12 clones recognized the TPO immunodomina
nt region. Moreover, regardless of selection with N-TPO or DN-TPO, their he
avy and light chains were encoded by similar VDJ and V-kappa combinations.
One clone (DN4), isolated using DN-TPO, did not interact with the TPO immun
odominant region and its H chain derives from a different V-H gene. Althoug
h DN4 binds specifically to TPO, its affinity is low, unlike the high affin
ities of other human TPO autoantibodies. In conclusion, human monoclonal au
toantibodies that preferentially recognize denatured TPO could not be isola
ted from an immunoglobulin gene library despite selection with denatured pr
otein. Our findings demonstrate the bias of the human B cell repertoire tow
ards recognition of an immunodominant region on the conformationally intact
form of a major thyroid autoantigen.