Interferon-gamma and interleukin 4 gene expression in cows infected with Mycobacterium paratuberculosis.

OBJECTIVE

To determine whether clinical progression of paratuberculosis in cattle was associated with alterations in cytokine gene expression in affected tissues.

ANIMALS

5 uninfected adult Holstein cows, 7 adult Holstein cows naturally infected with Mycobacterium paratuberculosis that did not have clinical signs of disease, and 4 adult Holstein cows naturally infected with M paratuberculosis that had progressive clinical signs of infection.

PROCEDURE

Samples of ileum and cecal lymph nodes were obtained from each animal at the time of slaughter. A reverse transcriptase-competitive polymerase chain reaction assay was used to determine mRNA expression of interferon-gamma (IFN-gamma) and interleukin 4 in each sample.

RESULTS

Interferon-gamma gene expression was significantly higher in ileum and cecal lymph node samples from subclinically infected cows than from clinically infected cows.

CONCLUSIONS AND CLINICAL RELEVANCE

Progression of paratuberculosis to clinical stages is associated with reduced expression of IFN-gamma at site of infection. If immune response to M paratuberculosis can be manipulated so that IFN-gamma expression is increased, resistance to infection in cattle might be enhanced.