Lymphocyte subset proliferative responses of Mycobacterium bovis-infected cattle to purified protein derivative

Despite highly successful eradication efforts in several countries, Mycobac terium bovis infection of cattle remains a significant health concern world wide. Immune mechanisms of resistance to and/or clearance of M. bovis infec tion of cattle, however, are unclear. Recent studies have provided evidence supporting a role for CD4(+), CD8(+), and gamma delta TCR+ T cells in the response of cattle to M. bovis. In the present study, we utilized a flow cy tometric-based proliferation assay to determine the relative contribution o f individual lymphocyte subsets in the response to M. bovis infection and/o r sensitization with mycobacterial purified protein derivative (PPD). perip heral blood mononuclear cells (PBMC) from M. bovis-infected cattle prolifer ated in response to in vitro stimulation with M. bovis PPD. CD4(+) T cells and gamma delta TCR+ cells were the predominate subsets of lymphocytes resp onding to PPD. gamma delta TCR+ cells also proliferated in non-stimulated c ultures: however, the gamma delta TCR+ cell proliferative response of infec ted cattle was significantly (p < 0.05) greater in PPD-stimulated cultures as compared to non-stimulated cultures. Intradermal injection of PPD for co mparative cervical testing (CCT) induced a boost in the in vitro proliferat ive response of CD4(+) but not <gamma>delta TCR+ cells of infected cattle. Administration of PPD for CCT also boosted interferon-gamma (IFN-gamma) pro duction by PBMC of infected cattle following in vitro stimulation with M. b ovis PPD. Injection of PPD for CCT did not, however, elicit a proliferative or IFN-gamma response in cells isolated from non-infected cattle. These da ta indicate that CD4(+) and gamma delta TCR+ cells of M. bovis-infected cat tle proliferate in a recall response to M. bovis PPD and that the CD4(+) ce ll response is boosted by intradermal injection with PPD for CCT. (C) 2000 Elsevier Science B.V. All rights reserved.