Bovine serum albumin (BSA) as a reagent against non-specific immunogold labeling on LR-White and epoxy resin.

The purpose of this study was to examine how different incubation times with different concentrations of bovine serum albumin (BSA) affect the amount of non-specific immunogold labeling on epoxy sections and LR-White sections. Immunogold labeling was performed on epoxy sections and LR-White sections of renal tissue with IgG-deposits and fibrin clots, and the antibodies used were anti-IgG and anti-fibrinogen, respectively. The sections were incubated with different concentrations of BSA prior to application of primary antibodies, and the length of this pre-incubation step varied between 0 and 4 h. During the incubation with primary antibodies, BSA was added in the same concentration as in the pre-incubation step. The results showed that the non-specific labeling on the resin decreased significantly when the concentration of BSA or the length of the preincubation step was increased. The non-specific labeling was usually higher on the epoxy resin than on the LR-White resin when using the same conditions with respect to BSA. But, when the preincubation step with BSA lasted 4 h, the non-specific labeling was somewhat lower on epoxy resin than on the acrylic LR-White resin, without respect to the concentration of BSA. The specific labeling for both fibrinogen and IgG decreased slightly when the concentration of BSA and incubation time increased, probably due to the steric hindrance performed by BSA molecules on the section. Blocking procedures with at least 1 h incubation time for the blocking step with at least 5% BSA are recommended for both epoxy and LR-White sections.