Rabbit IgG antibodies against cord red blood cell membranes bind to complement receptor 1 (CD35).
We have previously shown that a subpopulation of cord/fetal red blood cells (RBC) binds rabbit IgG antibodies raised against cord RBC and absorbed on adult RBC (F-IgG), while control IgG, raised against and absorbed on adult RBC (A-IgG), fails to do so. In the present study, F-IgG maintained its binding to cord RBC surface antigens following absorption on spectrin but not after absorption on skeleton-stripped RBC membranes. Spectrin-absorbed F-IgG- but not A-IgG-affinity-purified material from cord RBC contained polypeptides with apparent MW of complement receptor 1 (CR1) allotypes. Moreover, on immunoblotting these polypeptides reacted with 125I-F-IgG as well as with 125I-anti-CR1 mAb, and binding of 125I-anti-CR1 mAb was inhibited by unlabelled F-IgG. In addition, cord RBC incubated with F-IgG prior to reaction with anti-CR1 showed decreased fluorescence intensity on flow cytometry. Taken together the results suggest that F-IgG binds to CR1 which shows increased expression/accessibility on a subpopulation of cord/fetal RBC.
Giuliani
A L
AL
Dipartimento di Medicina Sperimentale e Diagnostica, Sezione di Patologia Generale, Università di Ferrara, Italy.gla@ifeuniv.unife.it
Pora
R
R
Verenini
M
M
Unis
L
L
Graldi
G
G
Ferrari
L
L
Lanza
F
F
Wiener
E
E
Lutz
H U
HU
Vesce
F
F
Berti
G
G
D000818:Animals; D001667:Binding, Competitive; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000276:immunology* / Q000378:metabolism; D005312:Fetal Blood / Q000276:immunology* / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D007074:Immunoglobulin G / Q000276:immunology* / Q000378:metabolism; D011817:Rabbits; D017463:Receptors, Complement 3b / Q000276:immunology* / Q000378:metabolism
D007074:Immunoglobulin G; D017463:Receptors, Complement 3b