F.J. Bourne

Cellular and humoral defence mechanisms in mares susceptible and resistant to persistent endometritis.

Both random and directional migration of blood neutrophils from 9 mares susceptible to persistent endometritis were significantly less (p less than 0.05) than neutrophils from 8 resistant mares. Serum from susceptible mares had significantly more (p less than 0.01) chemotactic activity than serum from resistant mares. Although phagocytosis of yeast blastospores by blood neutrophils from 4 resistant and 3 susceptible mares was similar, uterine neutrophils from susceptible mares were significantly worse (p less than 0.01) at phagocytosis than uterine neutrophils from resistant mares. Uterine washings from 17 susceptible mares were significantly better at opsonising yeast blastospores than washings from 14 resistant mares; however, washings from both groups had a similar ability to promote killing of S. zooepidemicus by neutrophils. When an immunologically non-specific endometritis was induced, washings from 3 susceptible mares were significantly worse at promoting bactericidal activity by 144 h than washings from 4 resistant mares (p less than 0.01). Haemolytic complement activity was significantly greater (p less than 0.001) in washings from 17 susceptible mares than from 14 resistant mares. Induction of acute endometritis resulted in high levels of haemolytic complement activity in 2 of 3 susceptible mares at 24 and 144 h, but only in small increases in 4 resistant mares. Thus, some abnormalities in neutrophil function were detected and a possible defect in promotion of neutrophil bactericidal activity by uterine secretions from susceptible mares but there was no evidence for any deficiency in haemolytic complement activity.

Specific Immunological Unresponsiveness following Active Primary Responses to Proteins in the Weaning Diet of Piglets

Young piglets weaned onto soya diets frequently develop diarrhoea which may have a dietary and/or immunological component. Piglets abruptly weaned onto soya at 3 weeks of age developed levels of serum IgG anti-soya antibodies almost comparable to those induced by injection with soya protein in adjuvant at 7 weeks. In the piglets primed by feeding, no significant further increase in antibody occurred after subsequent systemic injection. In contrast, secondary responses were observed in age-matched animals, previously primed by injection, and primary responses were obtained in previously naive piglets. The results demonstrate the development of specific unresponsiveness to soya proteins in neonates fed soya, despite the occurrence of an initial vigorous immune response to the fed protein.

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.

Altered immune response to proteins fed after neonatal exposure of piglets to the antigen.

The weaning of piglets onto soya proteins at 3 weeks old normally results in an active response to the fed protein, as determined by the appearance of serum IgG antisoya antibody. This system thus allows the effects of manipulation on the response to a fed protein to be studied. In animals previously given 1 g of soya protein at birth, the magnitude of the antibody response to soya fed at 3 weeks was decreased, although similar amounts of the fed protein could be detected in serum. In addition, the relative affinity of the dominant interaction between antigen and antibody was reduced in these piglets by almost an order of magnitude. By comparison, the ability of piglets given soya at birth to respond to injected soya was not significantly reduced. These results indicate that the regulation of responses to fed and systemic antigens is largely separate. Very early oral exposure to antigen may affect the ability of neonatal animals to mount immune responses to, specifically, fed proteins while leaving the response to systemic antigen largely intact.

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.

The immune response to dietary antigens and its influence on disease susceptibility in farm animals

Transient hypersensitivity reactions of the intestinal immune system to dietary antigens result in increases in enterocyte turnover and villous atrophy. These changes occur in the intestine of the post weaned piglet and precede the proliferation of E. coli and the development of post-weaning diarrhea. We therefore postulated that a transient cell mediated immune response to dietary antigens may increase susceptibility to disease. The interaction of dietary and microbial antigens upon the gut immune system has been investigated in mice and pigs and it has been shown that both exert powerful regulatory effects upon each other.

Dietary Antigen Handling by Mother and Offspring

Sows were Ted ovalbumin (OvA) as a novel protein antigen either throughout gestation and lactation (G + L) or during tactation only (L). This resulted in a significant uptake of OvA into blood, colostrum and milk along with a specific IgG response. In piglets from the G + L group. OvA and antibodies to OvA were detected in serum after ingestion of colostrum. In a large proportion of these piglets OvA was still detected at 3 weeks of age. In she L group a significant proportion of the piglets responded to OvA whilst still suckling their mother.

Histochemistry of mucins of pig intestinal secretory epithelial cells before and after weaning

Two histochemical staining techniques, Alcian blue/PAS and high-iron-diamine/Alcian blue, which differentiated neutral from sulphated and sialylated acid mucins were applied to sections of duodenum, ileum, caecum, colon and rectum from pigs aged one day, 3 weeks and 10 weeks. In each age group, sulphated-acid mucins predominated at all sites, particularly in the large intestine. In both the small and the large intestine, non-sulphated mucins occurred mainly at the bases of the crypts. Neutral mucins occurred in a few goblet cells in crypts and villi, either alone or together with acid mucins; neutral mucins increased away from the bases of the crypts. No changes were noted in the caecum, colon or rectum of pigs one, two, 5 or 13 days after weaning onto a diet containing soya protein. In the small intestine, there was a transient increase in the numbers of goblet cells in the crypts and villi, a relative increase in sulphated and a decrease in non-sulphated acid mucins and a change in the distribution of sulphated mucins in the crypts. No change in proportions of neutral and acid mucins was detected.

An enzyme-linked antiglobulin test for the detection of erythrocyte-bound antibodies in canine autoimmune haemolytic anaemia

A method has been developed which allows identification and quantitation of red cell-bound immunoglobulins and complement in canine blood. The technique utilizes ELISA methodology and the assay identifies cases of autoimmune haemolytic anaemia which are negative by the Direct Coombs test. Further, the amount of antibody present on the red cells shows a close correlation to the haemoglobin level; suggesting that the degree of sensitization of the RBCs influences their rate of destruction. Favourable response to treatment correlates with a decrease in the levels of bound antibody and complement.

The distribution of mucosal lymphoid nodules in the equine respiratory tract.

Mucosal lymphoid nodules were identified within the equine respiratory tract by an acetic acid fixation technique. Nodules were identified in foetuses from nine months gestational age, and estimates of total and regional nodule populations were made in foetal, neonatal and adult horses. Nodules occurred at specific sites within the tract, which probably relate to areas where inhaled antigens accumulate. The largest populations of nodules occurred in the nasopharynx and larynx, with smaller numbers in the nasal cavity, trachea and bronchi. There was an age-related change in the size of these nodule populations, with an increase in number from late gestation to the neonatal period to early adulthood (up to 5 years of age), followed by a decrease in older adults.