Role of EAC1q4 in C1a transfer reaction (C1aTR) and further information on the nature of the EAC1q4 site.

: The complement intermediates EAC1, EAC4, and EAC1q4 were prepared with guinea pig, porcine, as well as human complement. EAC4 and EAC1q4 were made from EC4 and EAC14 respectively. The C1a transfer reaction (C1aTR), the second step of Borsos' C1a fixation and transfer test, was carried out with various combinations of these intermediates. It was found that the EAC1q4, instead of the EAC4, was the C1a acceptor, and the C1rs subcomponents rather than the whole C1 molecule should have to transfer in the C1aTR. The EAC41 derived from EC4 generated no EAC1q4 in EDTA medium as the EAC14 did. This presented evidence for the joining of C4 to A in the EAC1q4 site.