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The influence of the route of vaccination on the systemic and local immune response has been studied in the sow with ferritin antigen using three methods of vaccination: 1. intramuscular with Freund’s complete adjuvant (FCA); 2. intramammary without FCA; 3. intramammary with FCA. Intramammary vaccination was found to be superior to intramuscular vaccination in producing both a local and a systemic response.

Immunological competence of the piglet fetus was demonstrated after the 55thday of gestation. The immunoglobulins involved were isolated and characterized. The main immunoglobulin was 19S IgM with smaller amounts of 7S IgG, 19S IgG, 4S IgG and 7S IgA. The possible clinical value of this finding is suggested.

Prostaglandins (pgs) F and E2were measured in lavage fluid from the uterus of ovariectomised mares after experimental induction of uterine inflammation. Treatment with progesterone alone, or progesterone followed by oestradiol, significantly increased the concentrations of these pgs in the lavage compared with mares treated with oestradiol or control mares. Ovarian steroids, therefore, influenced uterine pgsynthesis in response to an inflammatory stimulus. To determine whether the uterine lavage procedure might contribute to the concentrations of prostaglandins in the lavage, the procedure was also performed on six intact mares. With the exception of washings obtained at luteolysis, uterine concentrations of pgf(measured as the plasma metabolite 15-keto-13, 14-dihydro PGF2α) had returned to prewasning levels within 30 minutes of the start of uterine lavage. Lavage was therefore unlikely to have influenced the concentrations of prostaglandins in the lavage fluid.

A partly purified extract of granules from bovine neutrophils was used to investigate killing of mastitis pathogens by the non-oxidative killing system of the neutrophil. Eight strains of Staphylococcus aureus,two of Escherichia coliand two of Streptococcus uberiswere used. Different strains of bacteria had different sensitivities to killing by the extract, three strains of staphylococci being particularly resistant. Whereas E coliwere killed most effectively at pH 6·0, little or no killing of S aureustook place below pH 6·5 and, although S uberiswere also killed better above neutral pH, significant killing also took place at acidic pH levels. Resistance to killing by the extract was not significantly correlated with that by intact neutrophils.

The influence of arachidonic acid metabolites on migration of equine neutrophils under agarose was investigated. Leukotriene B4(ftb4) was chemotactic at concentrations between 0·1 and 1000 ng ml−1and prostaglandin E2(pge2) at 1 and 10 ng ml−1but not at higher or lower concentrations. Prostaglandin F2α(pgf2α) was not chemotactic for equine neutrophils at any concentration. Random migration was significantly inhibited (P<0·05) by suspension of neutrophils in ltb4(0·1 to 1000 ng ml−1). Migration was also inhibited (P<0·05) by suspension in low concentrations of pgf2(0·1 and 1 ng ml−1) and pgf2α(0·1 ng ml−1) but not at high concentrations. There was a significant positive correlation between random migration of neutrophils suspended in uterine washings from persistently endometritic mares and concentrations of endogenous PGF (P<0·002) and pgf2(P<0·05) in washings. Thus certain metabolites of arachidonic acid affect migration of equine neutrophils and may play a significant role in recruitment of neutrophils to sites of inflammation in the horse.

Antibody in serum, uterine and vaginal secretions was measured following local immunisation and experimental infection with the organism of contagious equine metritis (Taylorella equigenitalis). Intrauterine immunisation with killed T equigenitalisstimulated a systemic IgG titre and a uterine IgA and IgM response. Subsequent challenge with the organism, however, resulted in a characteristic metritis in both control and vaccinated mares. Antibody in serum and secretions was increased following challenge infection, dwarfing the response to immunisation. The local response was restricted to the IgA and IgM classes in both uterine and vaginal secretions. There was no elevation in local IgG antibody, although there was an increase in serum IgG in response to challenge infection. A second experimental challenge, following natural resolution of the initial infection and a period of reimmunisation, resulted in reduced clinical signs and bacterial isolation rates from both control and vaccinated mares, but no absolute protection from infection.

When 47 pigs were dosed orally with cultures of Treponema hyodysenteriae,44 (94 per cent) developed swine dysentery. Of those which recovered and were rechallenged, nine of 21 (43 per cent) showed clinical signs, as did one of 10 (10 per cent) challenged on a third occasion. Clinical disease was associated with development of specific IgG, IgA and IgM antibodies in serum and the local production of IgA in gut mucosal tissues. The appearance of antibody was not directly related to protection but rather indicated either prolonged exposure (in the case of serum IgG) or recent exposure to T hyodysenteriae(for secretory IgA). Infection also resulted in the appearance of IgG and IgA memory cells in gut-associated lymphoid tissue. However, these studies indicated that humoral immunity alone is not responsible for the onset of a protective response to T hyodysenteriaein the colon.

Pigs weaned at three weeks old absorb food protein antigens from the intestine. The amount of antigen absorbed declines over the next three weeks, and this decline is associated with an increasing level of serum antibody to the fed proteins. There was no difference in the rate of immune elimination of intravenously injected antigen in fed and unfed controls. The reduction of serum antigen is thus likely to reflect reduced absorption, possibly mediated by locally produced antibody. Pigs weaned at 10 weeks old also absorbed antigens and produced an antibody response when introduced to soya; and after three weeks of feeding soya the absorption of antigen was substantially reduced. This latter exclusion was specific for soya as a second novel protein (ovalbumin) was absorbed when introduced to the diet at this time. At six months, pigs no longer absorbed soya proteins when they were introduced to the diet. Furthermore, pigs of this age had serum ‘antibody’ to soya and other proteins such as keyhole limpet haemocyanin to which they had never been exposed.

An indirect immunoperoxidase technique was used to demonstrate both free immunoglobulin and immunoglobulin-containing plasma cells of IgG, IgA and IgM classes in the mucosa of the equine respiratory tract. IgA-producing plasma cells predominated in the upper airways, whereas IgG-producing cells predominated in the lower respiratory tract. IgM-secreting cells were uncommon, but present in their highest numbers in the nasopharynx. Plasma cells specific for all of the immunoglobulin classes were identified in the surface epithelium, lamina propria connective tissue, glandular tissue and organised lymphoid tissue. The surface epithelium stained strongly for free IgA and IgM, but weakly for IgG, whereas glandular cells and the lamina propria connective tissue stained most strongly for IgG.