Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/10/2000
Publication Date: N/A
Citation: Interpretive Summary: Despite highly successful eradication efforts in several countries, tuberculosis of cattle remains a serious health concern worldwide. While diagnostic reagents are available, improved techniques are needed for earlier detection of infected cattle. A better understanding of host responses to infection, however, is needed to develop improved methods of diagnosis. In this study, specific cell types responding to the bacterium within infected cattle were determined as well as those cells responding to diagnostic reagents administered to infected cattle. Knowledge obtained from this study will assist in the development of new reagents for the early detection of tuberculosis infection of cattle.
Technical Abstract: Despite highly successful eradication efforts in several countries, Mycobacterium bovis infection of cattle remains a significant health concern worldwide. Immune mechanisms of resistance to and/or clearance of M. bovis infection of cattle 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. We utilized a flow cytometric-based proliferation assay to determine the relative contribution of individual lymphocyte subsets in the response to M. bovis infection and/or sensitization with mycobacterial purified protein derivative (PPD). Peripheral blood mononuclear cells (PBMC) from M. bovis-infected cattle proliferated in response to in vitro stimulation with M. bovis PPD. CD4+ T and gamma/delta TCR+ cells were the predominate subsets of lymphocytes responding. Gamma/delta TCR+ cells also proliferated in nonstimulated cultures; however, the gamma/delta TCR+ cell proliferative response of infected cattle was significantly (P less than 0.05) greater in PPD- stimulated cultures as compared to nonstimulated cultures. Intradermal injection of PPD for comparative cervical testing (CCT) induced a boost in the in vitro proliferative response of CD4+, but not gamma/delta TCR+ cells of infected cattle. Administration of PPD for CCT also boosted interferon-gamma production by PBMC of infected cattle following in vitro stimulation with M. bovis PPD. Injection of PPD for CCT did not elicit a proliferative or IFN-gamma response in noninfected cattle. These data indicate that CD4+ and gamma/delta TCR+ cells of M. bovis-infected cattle proliferate in a recall response to M. bovis PPD and that the CD4+ cell response is boosted by intradermal injection with PPD for CCT.