Cytokines in pigs bred selectively for high and low immune response

Cytokine mRNA was studied by quantitative reverse transcription polymerase chain reaction utilizing an internal control for interleukin (IL)-1[alpha], IL-2, IL-4, IL-6, IL-8, IL-10, p35 and p40 subunits of IL-12, tumor necrosis factor (TNF)-[alpha], TNF-[beta] and interferon (IFN)-[gamma] and beta 2-microglobulin ([beta]2-m). Cytokine and [beta]2-m mRNA expression in pig blood cells stimulated by mitogens 'in vitro' was used to validate the method. Mitogens [phytohemagglutinin-P (PHA-P) and bacterial lipopolysaccharide (LPS)] induced characteristic responses. Interleukin-2 and IFN-[gamma] were more in PHA-P than LPS-treated cultures and IL-4 and TNF-[beta] were absent from the latter. Stimulation of lymph nodes with PHA-P and LPS induced distinct responses in efferent lymph cells. 'In vitro' and 'in vivo' responses were correlated for some cytokines. Lymph node stimulation with purified protein derivative of tuberculin (PPD) or hen egg white lysozyme did not induce cytokine patterns equivalent to murine T helper (Th)-1 and Th2 as IL-2 and IL-4 were absent. Cytokines in PPD-induced delayed-type hypersensitivity were also not preferentially Th1 as in other species. At generation 8 of selection, high (H) and low (L) immune response pigs were infected with 'Mycoplasma hyorhinis'. Arthritis was more severe in H than L pigs with more ' M. hyorhinis' colony forming units (cfu) in synovial fluid (SF). Line-related differences were not significant for cytokine production, but H pigs tended to produce more IL-6 and IFN-[gamma] than L in SF and synovial membrane (SM) mononuclear cells (MNCs), respectively. Arthritic lesion and cfu scores were positively correlated with IL-1[alpha], IL-6, IL-8, IL-10, TNF-[alpha], and IFN-[gamma] in SF or SM MNCs from arthritic but not from non-arthritic joints suggesting a role for these cytokines in the occurrence of arthritis. Since H pigs had severe arthritis with more 'M. hyorhinis' cfu than L, cytokine production may be related to the growth of 'M. hyorhinis ' thus contributing to the pathogenesis of arthritis.