Immunofluorescent and ultrastructural analysis of plasma cell degeneration in the chicken Harder's gland.

In this study we describe some aspects of plasma cell degeneration in the chicken Harder's gland. The immunofluorescent patterns of cytoplasmic immunoglobulin (cIg) localization have been studied in relation to the ultrastructure of maturing and degenerating B cells. It appears that Russell body formation through the accumulation of Ig within the cisternae of the rough endoplasmic (RER) does not represent the only mechanism for the formation of cytoplasmic vacuoles. Mitochondrial swelling and disruption or dilation of Golgi cisternae, often preceding alterations of the RER, may be the origin of some vacuoles. It also appears that, in the Harder's gland, degeneration may occur not only in mature plasma cells but also in maturing B cells at a stage when only clusters of polyribosomes are found in the cytoplasm and no RER is yet developed. These observations are relevant to some immunofluorescence and ultrastructural patterns observed in human B-cell pathology.