Distribution of immunoglobulins in equine tissues by indirect immunofluorescence

Monospecific rabbit antisera directed against the heavy chains of horse IgG a, IgG b, IgG c, IgA, IgB, IgG(T) and IgM were employed as reagents in the indirect immunofluorescent staining of horse tissues. Cells showing cytoplasmic staining for specific equine immunoglobulin heavy chain types could be identified and their distribution in horse parotid and submaxillary glands was compared with that obtained for the parotid and mesenteric lymph nodes as well as duodenum. Immunofluorescent staining of parotid and mesenteric lymph node sections revealed cells showing cytoplasmic fluorescence for IgG a, IgG b, IgG c and IgM among lymphoid cells comprising the core of germinal centres and medullary cords. IgA and IgG(T) staining was localized in cells predominantly situated in the cortex and around the periphery of germinal centres. Cells showing specific cytoplasmic staining for IgB were not found in sections of salivary glands or duodenum. Rare, isolated, single cells containing IgB immunoglobulin were encountered in cortical areas of parotid and mesenteric lymph nodes. Salivary glands stained for IgA showed localization of IgA immunoglobulin in individual cells of the acinar and ductular epithelium as well as in the cytoplasm of interstitial plasma cells. Heavy deposits of IgA were found within duct lumina. IgA, IgG (a,b,c) and IgG(T) were localized intercellularly in the interstitial connective tissue of salivary glands.