C. Proulx et al., HUMAN MONOCLONAL FAB FRAGMENTS RECOVERED FROM A COMBINATORIAL LIBRARYBIND SPECIFICALLY TO THE PLATELET HPA-1A ALLOANTIGEN ON GLYCOPROTEIN IIB-IIIA, Vox sanguinis, 72(1), 1997, pp. 52-60
Background and objectives: Certain clinical conditions are related to
the presence of platelet-specific alloantibodies in the patient's seru
m. We studied the molecular diversity of HPA-1a antibodies to analyze
some peculiarities of this antibody response. Materials and methods: H
uman antibody Fab fragments that bind to the platelet alloantigen HPA-
1a on glycoprotein IIb-IIIa (GPIIbIIIa) were generated by using a reco
mbinant phage display system. We established an immunoglobulin G1, kap
pa combinatorial library from the peripheral blood lymphocytes of a pe
rson undergoing a severe posttransfusion purpura. Results: Characteriz
ation of Fab clones selected from the fifth round of antigen-specific
panning of this library demonstrates a highly specific reactivity to t
he HPA-1a alloantigen. The nucleotide sequence analysis of representat
ive HPA-1a-specific clones reveals at least 3 distinct V-L and 3V(H) g
ene segments that present an extensive degree of mutation as demonstra
ted by comparison of gene usage and homologies to the nearest germline
genes. Conclusions: These human HPA-1a-specific Fab reagents should a
llow us to better understand the molecular mechanism involved in HPA-1
a alloimmunization.