Effect of antigen charge on immune complex interaction with glomerular cells in culture

The effect of antigen charge on immune complex (IC) interaction with glomerular cells was evaluated using cultured rabbit glomerular cells. Rat albumin (Alb) was modified to produce a cationic charge; isoelectric point (pI) 7.4-8.0; anionic charge, pI 4.0-4.2; or left unmodified, pI 6.2-6.4. I125-IC (100 micrograms Alb in complex) was incubated with cells for 44 hr. Cationic Alb IC (CAT IC) interaction was 7 and 10 times greater than unmodified (UM) and anionic (AN) IC, 7596 +/- 613 vs 1016 +/- 176 and 746 +/- 106 pg I125-Alb/micrograms cell protein, mean +/- SE (P less than 0.01). A 10-fold excess of unlabeled CAT Alb decreased CAT IC interaction (6342 +/- 432 vs 1246 +/- 296 pg I125-Alb/micrograms cell protein, P less than 0.01) increased UM IC (981 +/- 186 vs 3994 +/- 394 pg I125-Alb/micrograms cell protein, P less than 0.01), and had no effect on AN IC. A 10-fold excess unlabeled CAT IC increased interaction of both CAT IC (7067 +/- 514 vs 37,416 +/- 3026 pg I125-Alb/micrograms cell protein) and UM IC (994 +/- 123 vs 12,922 +/- 566 pg I125-Alb/micrograms cell protein) but not of AN IC. Incubation of cells with CAT, UM, or AN Alb followed by specific antibody demonstrated increased antibody interaction with cells exposed to CAT Alb (15,212 +/- 676 vs 3866 +/- 406 and 1785 +/- 206 pg I125-IgG/microgram cell protein for UM and AN Alb, respectively).