T.J. Newby

A study of cells in the mammary secretions of sows

The morphology and some of the in vitro functional properties of the cells in the mammary secretions of sows have been examined. A mean cell yield of 1 x 10(7) cells/ml was obtained from sow colostrum but during the first week post-partum the yield decreased approximately 10 fold. The polymorphonuclear leucocyte was the predominant cell type in colostrum and milk and was associated with varying proportions of lymphocytes, macrophages and epithelial cells. The phagocytes of sow milk ingested heat-killed yeast, although the phagocytic index for milk macrophages was low compared with autologous neutrophils and alveolar macrophages. Milk whey provided an effective opsonising medium for yeast ingestion. Intra-mammary immunisation of sows with ovalbumin induced antigen-reactive lymphocytes in both peripheral blood and milk.

Antibody Response of the Lactating Sow to Oral Immunization with Escherichia coli

Oral immunization of the lactating sow with live Escherichia coli (O8:K88)‐stimulated an IgA anti‐K88 antibody response in mammary Secretions and significantly enhanced the capacity of whey to inhibit adhesion of the inoculum E. coli strain to isolated pig enterocytes. An increase in agglutinating anti‐08 activity was also evident in milk and was associated with both the IgA and IgM immunoglobulin classes These mulls are consistent with the conceal of a gut mammary link, although measurement of specific antibody in the intestinal secretion of these animals suggested that there may be a difference in response duration at the two secretory sites. Prolonged oral administration of heat‐killed organisms also stimulated specific antibody synthesis within the mammary gland, although the response, particularly to the O antigen, was both reduced and delayed in its appearance.

Quantitation and origin of immunoglobulins A, G and M in the secretions and fluids of the reproductive tract of the sow

Immunoglobulin quantitation of fluids obtained from several regions of the female reproductive tract indicated the presence of IgG, IgA and IgM. IgG was almost invariably present in greatest amounts and IgM always made the smallest contribution. Although much of this immunoglobulin was derived from serum, evidence of the molecular size of IgA, the IgA and IgG ratios and that obtained from experiments involving the injection into sows of 125I-labelled immunoglobulin indicated that local synthesis within the tract also occurred.

The Immune Response Following Oral Vaccination with E. coli

The gut responds to colonisation by E. coli with a vigorous immune response principally involving the IgA class of immunoglobulin, which can be shown to protect against subsequent experimental challenge. In lactating sows there is a response also in the secretions of the mammary gland which is more prolonged than that in the intestine.

Altered Immune Function Associated with Dietary Factors

Mucosal presentation of antigens can promote both antigen specific (e.g. oral tolerance, immune exclusion) and antigen non-specific events (e.g. increased mucosal permeability to heterologous antigens). We have studied the antigen non-specific effects of two types of feeding regimes.

Transient Dietary Hypersensitivity in Mice and Pigs

In recent years, attention has focused upon the development of immune exclusion and oral tolerance as mechanisms that regulate and prevent damaging hypersensitivity reactions to dietary antigens. The significance of failure to develop these processes have similarly been investigated, it having been establshed that in the “mature response” to dietary antigens, local mucosal humoral immunity may co-exist with systemic tolerance, while both compartments of the cell mediated response are suppressed (1). It has long been known that following the introduction of a new dietary antigen, a transient serum response (2) may be induced; it is perhaps surprising, therefore, that the immunopathological significance of this early response to fed antigens has received little attention. Cell mediated responses may also be generated following feeding a wide range of antigens, including sheep red blood cells (SRBC) (3), ovalbumin (4) and contact sensitizing agents (5), as well as a wide range of infectious agents (6). In this study, we have induced transient cell mediated immune responses following feeding dietary antigens and determined the influence of “adjuvants” upon tolerance induction. The immunopathological consequence of this allergic response has been investigated in both mice and pigs.