Activation of the alternative pathway of complement by twelve different rabbit-mouse chimeric transfectoma IgA isotypes.
Previous experiments have resulted in the identification and cloning of 13 nonallelic genes encoding the constant region of rabbit IgA H chains. The genes, C alpha 1 to C alpha 13, were each cloned into an expression vector containing the VDJ gene of a dansyl (DNS)-binding murine hybridoma and the constructs were then transfected into SP2/0 cells that were producing murine kappa-L chains from the DNS-binding hybridoma. Of the 13 resulting transfectomas, 12 were shown, by ELISA, to secrete DNS-binding chimeric rabbit-mouse IgA molecules. These transfectoma antibodies, representing 12 different isotypes, are of high affinity and provide a unique source of Ag-specific IgA for comparison of the functions of the multiple IgA isotypes. One such function for antibodies is activation of C by either the classical or alternative pathway. We have used the DNS-binding IgA transfectoma antibodies in C assays based on binding of rabbit C3 to IgA-Ag complexes in an ELISA. The results demonstrated that all 12 IgA isotypes are capable of activating C by the alternative pathway but that none can activate C by the classical pathway. Control experiments demonstrated that activation was hapten dependent and was not caused by endotoxin contamination. These data demonstrate that Ag-specific IgA molecules, unmodified by heat or chemical aggregation, activate C by the alternative pathway but not by the classical pathway.
Schneiderman
R D
RD
Department of Microbiology and Immunology, University of Illinois, Chicago 60680.
Lint
T F
TF
Knight
K L
KL
D000818:Animals; D003001:Cloning, Molecular; D003167:Complement Activation; D003176:Complement C3 / Q000378:metabolism; D003170:Complement Pathway, Alternative; D007070:Immunoglobulin A / Q000276:immunology*; D007132:Immunoglobulin Isotypes / Q000276:immunology*; D066298:In Vitro Techniques; D051379:Mice; D011817:Rabbits; D011994:Recombinant Proteins; D014162:Transfection
D003176:Complement C3; D007070:Immunoglobulin A; D007132:Immunoglobulin Isotypes; D011994:Recombinant Proteins