The immunohistochemical detection of J chain in lymphoid cells in tissue sections: the necessity of trypsin digestion.

The immunohistochemical detection of J chain in histological sections of tonsils was compared to that of immunoglobulin IgG, IgM, and IgA. Pretreatment of tissue sections with detergents (saponin and Triton X-100) and with proteolytic enzyme (trypsin) at different experimental conditions has shown (i) 0.1% trypsin digestion for 1 hr at room temperature increased dramatically both the number of J-chain-positive cells detected, and the intensity of the color reaction, while the detergents had no noticeable effect; (ii) under the same conditions, trypsin also improved the detection of immunoglobulins, but quantitatively and qualitatively far less effectively than for J chain. The effect of trypsin occurred after 30 min. These results indicate that in tissue sections, the antigenic determinants of J chain are "masked" in the molecule of immunoglobulin in such a manner that the use of trypsin hydrolysis may be important for its successful detection at the light microscopic level. In the case of intact immunoglobulins, this is less important.