Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 3, 1996
Publication Date: N/A
Interpretive Summary: The nematode Ostertagia ostertagi is the predominant cause of parasite-induced production losses in cattle throughout temperate regions of the world. This predominance is partially due to the slow and incomplete development of protective immune responses. Cytokines are biologically active polypeptides that control the growth and differentiation of the immune cells responsible for protection. Herein we used two recently developed molecular assays to quantify mRNA levels for several important cytokines in cattle infected with O. ostertagi. We discovered in these experiments that after infection with the parasite, drastic changes in the cell composition of the lymph nodes at the site of infection accompanied by cytokine profiles of a Th2 type. Although this cytokine profile is associated with protection in other models, in the case of Ostertagia this profile did not correlate with protection. These findings represents an important step in identifying the basis for delayed development of protective immunity against this parasite.
Changes that occur in the local draining lymph nodes including, size of the nodes, changes in cell surface markers and cytokine gene expression were studied over the first 4 weeks of a primary, ostertagia ostertagi infection of the abomasum. Cells recovered from the abosamal lymph nodes (ABLN) after infection showed a decrease in the percentage of CD3+ cells, and an increase in the percentage of IgM+ cells and cells bearing the WC1 marker. These changes were coincident with an increase in both the size of the ABLN and the proportion of activated cells (CD25+). Analysis of mitogen-stimulated ABLN cells by RNase protection assay (RPA) showed a dramatic reduction in IL-2 and IFN-gamma transcription after infection. In addition, analysis of unstimulated ABLN cells by competitive RT-PCR showed a similar decrease in demonstrable levels of IL-2 mRNA, but IL-10, IL-4 and IFN-gamma mRNA levels were increased.