The potent IgG4-inducing antigen in banana is a mannose-binding lectin, BanLec-I.
IgG4 antibodies to banana were found to occur far more frequently than expected. The most important antigen involved proved to be a lectin, BanLec-I. Because of the lectin nature of the antigen, it was important to establish the antibody nature of the lectin-IgG4 interaction and to exclude an interaction between the sugar-binding site of the lectin and glycosidic chains on IgG4. Three arguments in support of immune binding are: (1) the binding of BanLec-I to IgG4 is mannoside resistant, whereas the binding to all other glycoproteins tested is mannoside inhibitable; (2) only a minor fraction of the IgG4 in serum and none of five IgG4 myelomas tested was bound, and (3) the lectin binds to the Fab fragment of the IgG4 molecule. A curious finding was that in the presence of high-molecular-weight glycoproteins the interaction between IgG4 and BanLec-I was enhanced by alpha-methyl mannoside. The probable explanation of this phenomenon is that complexes of the lectin with high-molecular-weight glycoproteins by sterical interference inhibit the interaction with human IgG4 antibodies (or with rabbit antibodies to the lectin). This inhibition is prevented in the presence of alpha-methyl mannoside. These results support the earlier suggestion that some lectins are particularly prone to induce an immune response upon oral feeding. This banana lectin might be a potentially useful carrier protein for oral antihapten immunization in humans.
Koshte
V L
VL
Central Laboratory, The Netherlands' Red Cross Blood Transfusion Service, Amsterdam.
Aalbers
M
M
Calkhoven
P G
PG
Aalberse
R C
RC
D000941:Antigens / Q000276:immunology*; D003176:Complement C3 / Q000502:physiology; D005638:Fruit / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000096:biosynthesis* / Q000276:immunology; D037102:Lectins / Q000276:immunology*; D008358:Mannose / Q000378:metabolism*; D008970:Molecular Weight; D037121:Plant Lectins
D000941:Antigens; C066788:BanLec-I; D003176:Complement C3; D007074:Immunoglobulin G; D037102:Lectins; D037121:Plant Lectins; D008358:Mannose