Identification of MHC II-restricted minor histocompatibility antigens after HLA-identical stem-cell transplantation.
BACKGROUND
After allogeneic hematopoietic stem-cell transplantation (HSCT), donor-derived T cells may elicit graft-versus-host disease (GVHD) and graft-versus-tumor (GVT) responses. The main targets of GVHD and GVT responses after human leukocyte antigen (HLA)-identical HSCT are minor histocompatibility antigens (mHAgs), that is, polymorphic gene products in which recipient and donor differ. Thus, for increasing beneficial GVT and decreasing life-threatening GVHD responses, knowledge of the relevant mHags is required. Here, we sought to identify mHags recognized by CD4 T cells using a novel serologic approach.


METHODS
To identify candidate mHAgs recognized by CD4 T cells, a cDNA expression library from peripheral blood mononuclear cells of a patient with β-thalassemia major was screened with serum taken at different time points after HLA-identical HSCT.


RESULTS
Immune responses against 18 antigens were identified with serum taken 100 days posttransplantation, when the patients had recovered from acute GVHD II. Except for one, no humoral responses against these antigens were detected 25 days or 1 year after transplantation. Sequence comparison of these antigens between recipient and donor revealed three polymorphisms of which two were contained within epitopes predicted to bind to HLA-DR molecules of the patient. Using cytokine secretion and capture assays, T cells specific for the polymorphic antigens of the recipient, but not the donor, were isolated from peripheral blood monocyte cells after HSCT.


CONCLUSIONS
The serologic approach described here facilitates the rapid identification of mHAgs recognized by CD4 T cells. Furthermore, the correlation of humoral and cellular immune responses with acute GVHD implies a role of these antigens in GVHD pathology.
Milosevic
Slavoljub
S
Clinical Cooperation Group, Helmholtz-Zentrum München, Munich, Germany.
Bachnick
Barbara
B
Karim
Karzan
K
Bornkamm
Georg W
GW
Witter
Klaus
K
Gerbitz
Armin
A
Mautner
Josef
J
Behrends
Uta
U
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D006086:Graft vs Host Disease / Q000276:immunology; D006680:HLA Antigens / Q000235:genetics / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000235:genetics / Q000276:immunology; D006650:Histocompatibility Testing; D006801:Humans; D015778:Minor Histocompatibility Antigens / Q000276:immunology*; D011110:Polymorphism, Genetic; D020641:Polymorphism, Single Nucleotide; D033581:Stem Cell Transplantation; D014019:Tissue Donors; D014184:Transplantation, Homologous / Q000276:immunology
D006680:HLA Antigens; D000949:Histocompatibility Antigens Class II; D015778:Minor Histocompatibility Antigens