TY - JOUR
T1 - Analysis of human C4A and C4B binding to an immune complex in serum
AU - Reilly, B. D.
PY - 1999
Y1 - 1999
N2 - Previous studies using isolated complement proteins have shown that more C4A than C4B binds to certain types of immune complexes. However, the in vivo binding of the C4 isoforms to an immune complex has not been investigated in detail and may differ from events when measured with the isolated proteins. We report here the binding of C4A and C4B to an immune complex of bovine serum albumin (BSA) anti-BSA as it occurs in serum. We found that when using the isolated C4 proteins more C4A than C4B bound to the complex, but in serum similar amounts of C4A and C4B were found to bind. Furthermore, these results were not explainable by a difference in activity between isoforms. In an attempt to explain these results a number of unexpected observations were noted. First C4A, but not C4B, bound specifically to a yet unidentified 38- kD serum protein. Second, when both covalent and noncovalent binding was assessed, we found that as serum concentration increased there followed a concomitant decrease in covalent binding and C4B was more affected than C4A. The potential biological significance of these findings is discussed.
AB - Previous studies using isolated complement proteins have shown that more C4A than C4B binds to certain types of immune complexes. However, the in vivo binding of the C4 isoforms to an immune complex has not been investigated in detail and may differ from events when measured with the isolated proteins. We report here the binding of C4A and C4B to an immune complex of bovine serum albumin (BSA) anti-BSA as it occurs in serum. We found that when using the isolated C4 proteins more C4A than C4B bound to the complex, but in serum similar amounts of C4A and C4B were found to bind. Furthermore, these results were not explainable by a difference in activity between isoforms. In an attempt to explain these results a number of unexpected observations were noted. First C4A, but not C4B, bound specifically to a yet unidentified 38- kD serum protein. Second, when both covalent and noncovalent binding was assessed, we found that as serum concentration increased there followed a concomitant decrease in covalent binding and C4B was more affected than C4A. The potential biological significance of these findings is discussed.
KW - C4
KW - Immune complex
KW - Systemic lupus erythematosus
UR - http://www.scopus.com/inward/record.url?scp=0033007491&partnerID=8YFLogxK
U2 - 10.1046/j.1365-2249.1999.00940.x
DO - 10.1046/j.1365-2249.1999.00940.x
M3 - Article
C2 - 10403910
AN - SCOPUS:0033007491
SN - 0009-9104
VL - 117
SP - 12
EP - 18
JO - Clinical and Experimental Immunology
JF - Clinical and Experimental Immunology
IS - 1
ER -