The nature of the local immune system of the bovine small intestine.

In an examination of the immunoglobulins of the small intestine of calve, IgG1 was the major immunoglobulin in the secretions, and IgA was present in smaller amounts. Immunohistochemical studies showed few IgA containing plasma cells but many cells that stained with anti-IgG antiserum. Histological evidence of transport of IgG1 across the crypt epithelial cell was found. Studies with 125I-labelled IgG1 indicated that a significant proportion of IgG1 in the intestine originated in serum.