SEARCH FOR THE ANTIGEN-SPECIFICITY OF HOMOGENEOUS IGG COMPONENTS (H-IGG) AFTER ALLOGENEIC BONE-MARROW TRANSPLANTATION

After allogeneic BMT, transient homogeneous Ig components (H-Ig) can b e detected in the sera of most graft recipients, So far, data on the a ntigen-specificity and therefore the function of these H-Ig are not av ailable, Such information may be important for our understanding of th e underlying mechanisms that are responsible for these excessive clona l B cell expansions, and it may help to delineate the functional antib ody repertoire after BMT, In the present study, sera of 98 paediatric BM graft recipients were investigated for the potential presence of H- Ig of IgG isotype (H-IgG) with specificity towards a panel of antigens , including vaccine and herpes virus antigens, auto-antigens and allo- antigens. The vast majority of H-IgG in sera of BM graft recipients we re unreactive when tested for this panel of antigens, However, in four cases, antigen-specificity of H-IgG to tetanus toroid could be demons trated after vaccination with that antigen, An explanation for the neg ative findings may be either that a restricted antibody production had been elicited by other non-tested antigens, eg substances of colonizi ng and translocating bacteria or of food antigens, or that the H-IgG c omponents may have antiidiotype or anti-'self' specificity.