Role of divalent cations in binding polymorphonuclear leucocytes to glomeruli with immune complexes.

The binding of polymorphonuclear leucocytes (PMN) to the glomeruli of rats in which glomerulonephritis had been induced by bovine serum albumin, suggested a biological activity of the immune complexes localized in the glomeruli. To evaluate divalent cations or serum factors which may be involved, a two-step method for PMN binding was introduced. PMN were suspended in serum-free media and incubated with cryostat kidney sections pretreated with divalent cation-chelated or fresh sera. An appropriate concentration of Mg++ was found to be essential for maximal PMN binding; however, Ca++ may represent a partial substitute for Mg++. Immune complexes localized in the glomeruli fix and activate the complement system via both the classical and the alternative pathways.