HEREDITARY C6 DEFICIENCY IN A STRAIN OF PVG C RATS/

A chance observation has led to the discovery of a strain of PVG rats (PVG/c(-)) which are deficient in complement (C) component C6. Analysi s of total haemolytic activity (CH50) of PVG/c(-) serum revealed an ab sent CH50 activity compared with serum of other rat strains and of a P VG/c rat (PVG/c(+)) that showed normal C activity. Thus, the PVG/c(-) rat was unable to activate the C5b-9 membrane attack complex. To gain insight into the complement abnormalities, analysis of individual C co mponents was performed. Testing the PVG/c(-) serum in a C6 haemolytic assay and using deficient human sera showed a deficiency of C6 in the PVG/c(-) rat. Highly purified human C6 and human sera deficient in oth er components were able to reconstitute the CH50 activity of the PVG/c (-) rat. The possibility that an inactivator of C was present in PVG/c (-) serum was excluded. The deficiency was found to be inheritable and under the control of an autosomal recessive gene. Furthermore, tissue antigens and immunity of the PVG/c(-) rat were found to be identical to those determined in the PVG/c(+) rat. With regard to their health s tatus, the PVG/c(-) animals seem to have no disadvantages compared wit h PVG/c(+) rats when held under the same conditions within the protect ed environment of animal facilities. Taken together, both rat strains provide an unique animal model for studying the biological role of C, particularly the C5b-9 membrane attack complex in experimental medicin e.