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The Effect of C4 on C1 Binding and Activation
Author(s) -
YMAN I. MALMHEDEN,
EIM G. STALENH,
SJÖQUIST J.
Publication year - 1982
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1111/j.1365-3083.1982.tb00688.x
Subject(s) - haemolysis , protein a , staphylococcus aureus , chemistry , antibody , cell , immunoglobulin g , biochemistry , enzyme , microbiology and biotechnology , biophysics , biology , immunology , bacteria , genetics
Cell‐bound human C4 enhances the uptake of CT by immunoglobulin‐carrying cells. The effect is more pronounced with small amounts of IgG than with large amounts. Furthermore, the presence of C4 on the cell surface dramatically promotes the enzymatic effect of C1 on C7. The C1 binding is efficiently blocked, and the C1 activation is almost abolished by pretreating IgG‐bearing cells with protein A from Staphylococcus aureus . In contrast, protein A has no effect on cells carrying C4 in addition to IgG. Protein A added in small amounts to IgG‐coated sheep erythrocytes inhibits the haemolysis by subsequently added human scrum, whereas even larger amounts of protein A has no effect when added to cells carrying C4 as well. Cells with and without C4 take up protein A equally well.