Age-related changes in porcine humoral and cellular immune parameters

The sequence of development of porcine systemic and local humoral and cellular immunity was analyzed by the age-dependent patterns of total serum immunoglobulin (Ig) levels, responsiveness of peripheral blood lymphocytes (PBL) to common mitogens (phytohemagglutinin, PHA; concanavalin A, ConA; poke-weed mitogen. PWM), or allogeneic PBL in a mixed lymphocyte culture (MLC), and the expression/distribution patterns of intestinal mucosal immune cell subsets, in order to establish the basic immune parameters for an assessment of immunocompetence in clinically normal pigs. Thus, we surveyed the species-related physiological values of these parameters in different age/technological categories, comprising infant (suckling and weaned pigs) and adult (gilts, sows, and boars) swine, kept in intensive rearing conditions. The highest level of total Igs was determined in neonatal pigs (43.5 +/- 4.6 g/L), and this value was significantly higher (P<0.001) than that in weaned pigs (12.1 +/- 1.5 g/L). Among adult swine, the highest level of total Igs was recorded in sows (32.0 +/- 3.1 g/L), and this was much higher (P<0.001) than that found in gilts (25.1 +/- 3.5 g/L) or boars (21.2 +/- 5.0 g/L). The reactivity of PBL in neonatal pigs decreased by 60-70% compared to weaned pigs, regardless of the stimulator applied. In adult swine, the strongest reactivity of PBL, except to PHA, was determined in sows. Histomorphometric analyses showed that CD45RA(+), CD45RC(+). and IgA(+) cells in sections of the jejunum and ileum were significantly higher in weaned pigs (P<0.05) compared to neonatal pigs. The immune parameters obtained for a sample of the swine population in Croatia may serve as a basis for further research on porcine systemic and local (intestinal) immune responsiveness regarding (i) differences among breeds, (ii) the influence of paragenetic factors, (iii) the impact of microbial etiology diseases, particularly those accompanied by immunosuppression, and (iv) the validation of specific/nonspecific immunomodulation.