Direct antigen binding to glomerular immune complex deposits.

We evaluated the contribution of intrarenal factors in the increased renal accumulation of bovine serum albumin (BSA) in chronic serum sickness (CSS). Renal transplantation was used to study 125I BSA uptake (single and paired label techniques) in normal and CSS kidneys exposed to the same immunologic milieu. In CSS, the daily dose of BSA (dose 15 to 150 mg) was substituted with radiolabeled BSA. Uptake in washed kidney homogenates (24 hours) in the recipient's native CSS kidney varied from 0.29 to 38.40 micrograms/g of kidney (mean 11.70) compared to 0.09 to 2.19 micrograms/g (mean 1.01) in the transplanted normal kidney. The ratio of uptake in the CSS/normal kidney varied from 2.1 to 17.5. These findings indicated that intrarenal factors were important in renal uptake since both kidneys had been exposed to the same circulating immune complex load. Transplantation between "early" (nonproteinuric) and late (proteinuric) CSS rabbits again suggested intrarenal factors influence the uptake of 125I BSA immune complex components with late CSS kidney/early CSS kidney uptake ratios of 25 and 49 in the pairs examined. When CSS kidneys were transplanted into normal rabbits, the binding of 1 to 160 mg of radiolabeled BSA in the transplanted CSS kidney varied from 0.68 to 22.89 micrograms/g (mean 7.15) compared to 0.01 to 0.84 microgram/g (mean 0.18) in the normal rabbit's native kidney. The uptake in the CSS kidney always exceeded that in the recipient's normal kidney (ratio varied from 18 to 289). The binding of radiolabeled BSA in the CSS kidney was quantitatively similar to that found previously in the intact CSS rabbit.(ABSTRACT TRUNCATED AT 250 WORDS)