tuberculosis-infected guinea pigs or animals with experimental tuberculous pleuritis enhanced splenic granuloma organization and inflammatory processes [20–25]. This is the first study that demonstrates that rgpTNF-α exerts immunomodulatory effects when injected after BCG vaccination in guinea pigs. The dose of TNF-α was selected on the basis of previous studies in mice [13,16,31]. TNF GS-1101 ic50 treatment was not associated with overt toxicity, as the guinea pigs did not display weight loss, morbidity or mortality. TNF-α is known

to mediate a number of immunological functions after M. tuberculosis infection including cell recruitment, induction of chemokine and cytokine secretion, macrophage activation and apoptosis, in addition to synergizing with IFN-γ in the formation and maintenance of granuloma [19,32–34]. Injection of guinea pigs with rgpTNF-α induced an increase in the PPD skin test response (Fig. 1a), suggesting that it may enhance leucocyte recruitment and/or other aspects of the dermal inflammatory responses at the site of antigen challenge in the M. bovis BCG-vaccinated animals. TNF-α treatment also resulted in an increase in the see more infiltration of mononuclear cells in the lymph nodes draining the vaccination site (Fig. 6), as well as an increase in the proportions of CD3+ T cells (Fig. 3a). An increase in CD3+

T cells after TNF-α treatment was not accompanied by an increase in the number of CD4 or CD8+ T cell subsets. One explanation for this result could be that while all α and β T cell receptor-positive T cells express CD3 antigen on their surface, cells other than CD3+ T cells, such as macrophages or dendritic cells, are also known to express CD4 or CD8 markers [35]. Thus, a concomitant change in the CD4 or CD8+ T cells may not be evident in these

experiments, and in future this can be addressed by the double staining of cells against CD3 and CD4 or CD8 T cell phenotypic markers. In addition, however antigen-specific T cell proliferation to PPD was enhanced in the lymph nodes of guinea pigs treated with rgpTNF-α, while Con-A-induced proliferation of T cells remained unaltered in these animals (Fig. 2c). The results from these in vivo studies are consistent with the in vitro observations reported earlier from our laboratory, that treatment with rgpTNF-α of spleen cells from BCG-vaccinated guinea pigs enhanced the T cell proliferation to PPD and not ConA [21]. The differential effect of TNF-α on PPD or ConA-induced T cell proliferation may be attributed to the differential contributions of co-stimulation by antigen-presenting cells (APC), as reported by others [36,37]. From our study, as well as from others, it is clear that TNF-α causes further proliferation of T cells but TNF blockade enhances both Th1 (IFN-γ and IL-12p40) and Th2 (IL-10) cytokine responses in mice with chronic tuberculosis infection [13,21].