Immunohistochemical identification of immunoglobulin A on ultrathin tissue sections

Antigenic determinants of the heavy chain of immunoglobulin A (IgA) were identified within immunocytes by immunohistochemical techniques applied to ultrathin sections of rat ileal mucosa embedded in eposy resin. Successful localization of IgA depended upon the utilization of chemical fixatives containing paraformaldehyde or physical fixation employing a freeze-drying technique. Partial removal of the epoxy resin from the ultrathin tissue section with metallic alkoxide solutions or pretreatment with H2O2 was essential prior to the sequential application of the immunological reagents. IgA was associated with the rough endoplasmic reticulum (RER) and nuclear regions of immunocytes. These results are similar to those of other investigators employing immunochemical localization before embedment.