The complement-activating capacity of maternal IgG antibodies to blood group A in paired mother/child serum samples.
OBJECTIVE
The aim of this study was to investigate whether IgG antibodies to blood group A bind or activate complement after crossing the placenta.


METHODS
IgG anti-A concentrations as well as C1-q-binding and the capacity of anti-A to form the C5b-9 membrane attack complex were measured in sera of 61 mother/child pairs. The enzyme-linked immunosorbent assay was used to quantitate anti-A or anti-B in maternal and neonatal serum samples.


RESULTS
The concentrations of IgG anti-A in ABO-identical and ABO-compatible children born to type O or B mothers correlated significantly with maternal concentrations (p < 0.05), whereas type A or AB children had strikingly diminished concentrations of IgG anti-A. The IgG anti-A concentrations were analyzed in two different groups: first, 44 mother/child pairs with mothers and children group O or B (group I), and second, 17 pairs with mothers group O or B and children group A or AB (group II). In group I, identical or compatible pairs with regard to IgG anti-A, a significant correlation was found by Spearman's rank analysis, whereas the same analysis revealed no significant correlation in group II. The capacity of anti-A to activate complement was also more marked in newborns who were ABO-identical or ABO-compatible with their mothers, and this capacity was virtually absent in cord blood samples from incompatible babies.


CONCLUSIONS
Tests for complement-dependent or complement-independent ABO blood group antibodies must be interpreted in the light of the blood group of the child.
Hari
Y
Y
Regional Blood Transfusion Center of the Swiss Red Cross, Switzerland.
von Allmen
E C
EC
Boss
G M
GM
Naiem
A
A
Gittermann
M
M
Nydegger
U E
UE
D000017:ABO Blood-Group System / Q000276:immunology*; D000888:Antibodies, Anti-Idiotypic / Q000097:blood / Q000276:immunology*; D003167:Complement Activation / Q000276:immunology*; D015922:Complement C1q / Q000378:metabolism; D015941:Complement Hemolytic Activity Assay; D015938:Complement Membrane Attack Complex / Q000096:biosynthesis; D005260:Female; D005312:Fetal Blood / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D007075:Immunoglobulin M / Q000097:blood / Q000276:immunology; D007231:Infant, Newborn; D007518:Isoantibodies / Q000097:blood; D008297:Male; D008431:Maternal-Fetal Exchange / Q000276:immunology; D011247:Pregnancy
D000017:ABO Blood-Group System; D000888:Antibodies, Anti-Idiotypic; D015938:Complement Membrane Attack Complex; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D007518:Isoantibodies; C048844:anti-IgG; D015922:Complement C1q