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Abstract

The purpose of this study was to examine the intensity of the immunogold labeling of kappa light chains as single molecules and as parts of whole immunoglobulin molecules in LR-White sections and epoxy sections both practically and theoretically. Human renal tissues including deposits of kappa light chains and immune complex deposits of IgA were embedded in both LR-White resin and epoxy resin. Immunogold labeling was performed on unetched thin sections of both resins with anti-κ or anti-IgA. In all relevant cases the immunolabeling was intense on the LR-White sections. Single kappa light chains were intensely labeled also on the epoxy sections, although not as intensely as on LR-White sections. In contrast, the immunogold labeling of whole immunoglobulins with anti-κ and anti-IgA was weak and hardly positive on the epoxy sections. Consequently, the quotient labelinglr-white/labelingepoxy for anti-κ was significantly lower for labeling of single light chains (3.6) than for labeling of whole immunoglobulins (15.9). The corresponding quotient for labeling of whole immunoglobulins with anti-IgA was 17.0. Supported by theoretical considerations, it is believed that the copolymerization between the epoxy resin and the antigens allows the knife to cleave the large whole immunoglobulins more easily than the smaller single kappa chains. This prevents satisfactory immunolabeling of whole immunoglobulins on epoxy sections whether anti-κ or anti-IgA is used as antibodies, while single kappa chains are easily immunolabeled.