Regulation of C3 deposition on gp120 coated CD4 positive cells by decay accelerating factor and factor H.
We investigated complement activation by recombinant gp120 (rgp120) treated CD4 cells and the role host complement regulatory proteins play in controlling C3 deposition. Complement activation was determined by detection of C3 on rgp120 coated cells in the presence and absence of HIV seropositive sera using flow cytometry. Treatment of rgp120 coated cells with complement resulted in C3 deposition only if HIV positive sera was included. Examination of C3 fragments on these cells demonstrated rapid cleavage of C3b to iC3b. The role of the regulatory proteins was examined by pretreating cells with mAb to block decay accelerating factor (DAF) or membrane cofactor protein (MCP) or by using factor H depleted sera as a complement source. Inhibition of DAF or use of factor H depleted sera significantly increased C3 deposition on rgp120 coated cells. In contrast, C3 deposition on rgp120 coated cells was not increased after blocking MCP. The sensitivity of rgp120 coated cells to complement lysis was unchanged after inhibition of the regulatory proteins, despite the increase in C3 deposited. These results indicate that in a model of virus infected cells, C3 deposition is regulated by DAF and factor H but MCP appears to have no role.
Sadlon
T A
TA
Department of Microbiology and Infectious Diseases, Flinders Medical Centre, Bedford Park, Australia.
Parker
S J
SJ
Gordon
D L
DL
D015703:Antigens, CD / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D018958:CD55 Antigens; D002460:Cell Line; D003167:Complement Activation; D003176:Complement C3 / Q000378:metabolism*; D017242:Complement Factor H / Q000378:metabolism; D003171:Complement Pathway, Classical; D003602:Cytotoxicity, Immunologic; D015699:HIV Envelope Protein gp120 / Q000276:immunology*; D006801:Humans; D066298:In Vitro Techniques; D008562:Membrane Glycoproteins / Q000378:metabolism; D011994:Recombinant Proteins
D015703:Antigens, CD; D018958:CD55 Antigens; C493495:CFH protein, human; D003176:Complement C3; D015699:HIV Envelope Protein gp120; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; D017242:Complement Factor H