English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Many properties have been associated with Pasteurella haemolytica leukotoxin and other repeat-in-toxin toxins, including their cytotoxic activity on various cells of the lymphoid and nonlymphoid systems as well as their ability to modulate the immunological activity of lymphocytes and monocytes. In this study, we assessed the ability of P. haemolytica leukotoxin to affect the expression major histocompatibility complex (MHC) class II molecules on bovine peripheral monocytes. Peripheral blood mononuclear cells were isolated from P. haemolytica leukotoxin-seronegative calves and incubated with various concentrations of authentic leukotoxin as well as the recombinant lktA gene product (LktA). Expression of MHC class II antigen on cells was evaluated by flow cytometric methods. The results indicated that both a crude, authentic leukotoxin preparation and LktA were able to affect MHC class II expression by inducing a marked downregulation of MHC class II expression on bovine monocytes. However, when cells were activated with gamma interferon (IFN-gamma), LktA and Lkt had little or no detectable effect. By using a cell line which expresses MHC class II only after activation by INF-gamma, we were able to confirm the observation that LktA had no effect on the expression of MHC class II after IFN-gamma treatment. Leukotoxin affected the functional capacity of monocytes to present antigen, as demonstrated by the ability of LktA or authentic leukotoxin to totally inhibit a mixed lymphocyte culture from MHC-mismatched calves. Thus, leukotoxin was able to downregulate constitutive expression of MHC class II expression, and we propose that this is a novel way in which this molecule can affect the immune function of monocytes, playing an important role in bacterial pathogenesis and survival of organisms at the infection site.

Regulation of major histocompatibility complex class II expression by Pasteurella haemolytica leukotoxin