In vitro evaluation of porcine lymphocyte response to phytohaemagglutinin using a modified "whole blood" technique

Variation in the immune status of two Australian pig breeds

OBJECTIVE

To investigate the variation in immune competence of two Australian pig breeds.

DESIGN

A panel of immune tests were used to assess breed and sire differences in weaner piglets of Large White and Duroc breeds.

PROCEDURE

All piglets were immunised against porcine leptospirosis. Blood samples were taken for studies on lymphocyte phenotypes, mitogenic responses of blood cells and serological analysis.

RESULTS

Significantly larger blood leucocyte numbers were found in Large White piglets compared with Duroc piglets after vaccinations. No significant difference in concanavalin A induced blood cell proliferation was found between these two breeds before or after vaccinations. Some significant breed variation in blood lymphocyte phenotypes was found. While the age-related changes of lymphocyte phenotypes were similar for the two breeds, the Large White breed had significantly larger numbers of CD2+ and CD4+ cells than the Duroc breed after the two vaccinations. There were also significant sire effects on CD8+ cells within the Large White breed after the first vaccination. No significant breed difference was detectable in serum IgG concentrations but sire differences within each breed before the primary vaccination were found. The serum antibody response to vaccination against leptospirosis was generally small, and showed no variations due to either breed or sire. No gender effects were found during the entire study.

CONCLUSION

The study demonstrated significant differences in some important immune components of the pig breeds studied. This may in turn indicate the variation in their immune competence or disease resistance. However, further investigation into the heritability and correlation with specific immune responses is required.

Mitogenic reactivity of mononuclear cells isolated from thymus, spleen and umbilical cord blood of pig foetuses

The in vitro mitogenic reactivity of mononuclear cells from the thymus, spleen and umbilical cord blood of Danish Landrace pig foetuses ranging in gestational age (GA) from 48 to 112 days was monitored by means of a microculture lymphocyte transformation test (LTT). Dose-response profiles for concanavalin A (Con A), pokeweed mitogen (PWM) and leucoagglutinin (LAG) were set up for the various age-groups and the results showed that the onset and development of mitogenic reactivity in the pig foetus is age-related. The results indicate the occurrence of mitogen responsive cells in the thymus and cord blood at 48 days GA and in the spleen at 54 days but statistically significant reactivity (p less than 0.01) for the various tissues could only be demonstrated at later stages of gestation. Thymus cells from all foetuses ranging in GA from 54 to 112 days exhibited significant reactivity to Con A, PWM and LAG. While the first detectable definite response of spleen cells was seen at 60 days GA when 50% of the foetuses exhibited significant reactivity to the 3 mitogens, spleen cells from all foetuses beyond that age responded significantly. Cord blood cells from only 50% of the foetuses of 60 and 70 days GA responded significantly to Con A and PWM but after this stage, cord blood cells from all foetuses did. The first significant response of cord blood cells to LAG was seen at 70 days GA but only in 50% of the foetuses and it was not until 100 days GA that significant reactivity to LAG was detected in all foetuses.

Aujeszky's disease vaccination and infection of pigs with maternal immunity: effects on cell- and antibody-mediated immunity

SCC, ADV-SCC, ADV-ADCC and ADV-LYST as well as ND50-titres of neutralizing serum antibodies were examined in 36 passively immune pigs, 25 of which were vaccinated at 3 weeks of age and partly revaccinated 3 weeks later. Twenty-five vaccinated animals and 8 non-immune control pigs were challenged with infectious ADV. Independent of the state of maternal immunity the cytotoxic response of the white blood cells from all the animals was low at WPP 3 but rose with increasing age. ADV-LYST occurred only in some of the animals. A single vaccination evoked no significant effect on our immune parameters, but revaccination led to higher ADV-LYST and ADV-ADCC. In pigs vaccinated at WPP 3 the neutralizing serum titres decreased gradually, similar to unvaccinated animals, indicating that the antibodies were of maternal origin. However, after vaccination at WPP 6, no further decline of ND50-titres could be detected, pointing to a limited antibody production. Animals vaccinated at WPP 3 and revaccinated 3 weeks later showed a significant increase of serum neutralizing titres. Whereas the controls showed typical symptoms of Aujeszky's disease, the immune animals, especially the unvaccinated passively immune pigs, showed only elevated temperatures and most of them excreted small amounts of ADV. The development of cellular immunity after infection was rather similar within the maternally immune group independent whether the animals had been vaccinated or not, but ADV-ADCC and ADV-LYST showed a more rapid progress within the vaccinated group than in the non-vaccinated group and the non-immune control group. Infection resulted in significantly higher ND50 titres in vaccinated and revaccinated animals than in unvaccinated animals, indicating a secondary response in those pigs. Thus, ADV sensitization of lymphocytes had been evoked by vaccination despite the presence of maternal antibody. The interpretation of the results was complicated by great individual and litter-dependent variations of the immune parameters.

Optimal conditions for in vitro blastogenesis of feline peripheral blood lymphocytes

A microculture technique was developed for the in vitro blastogenesis of feline lymphocytes. Blastogenesis of ficoll-diatriazoate gradient separated mononuclear cell, washed blood and whole blood were compared. In general the whole blood cultures yielded higher stimulation indices (SI) than the washed blood or separated mononuclear cell cultures. The effect of several variables on the stimulation of lymphocyte cultures was examined. A cell concentration of 3 x 10(5) cells/well and a 1:20 dilution of washed and unwashed whole blood gave optimal stimulation with concanavalin A (Con A). Phytohaemagglutinin-P (PHA-P) did not give significant levels of stimulation. Inactivated fetal calf serum (FCS) at levels of 2.5% (for washed blood) and 5% (for separated mononuclear cell and whole blood) gave highest SI. Supplementation with FCS was preferable to autologous, homologous or horse sera for all cultures. Optimal SI was obtained in all cultures incubated for 3 days and labelled with 1 microCi tritiated thymidine (3H-TdR) for the last 16 hours. The highest SI were in the range of 70 to 105 (18,764 to 42,681 counts per minute (CPM) for separated mononuclear cell culture, 100 to 165 (28,403 to 45,334 CPM) for washed blood culture and 105 to 186 (41,076 to 69,999 CPM) for whole blood culture.