Early events leading to the host protective Th2 immune response to an intestinal nematode parasite /

by Pesce, John Thomas

Title of Thesis: Name Thesis Directed by: Early Events Leading to the Host Protective Th2 Immune Response to an Intestinal Nematode Parasite John Thomas Pesce William C. Gause, Ph.D. Vice Chair, Department of Microbiology and Immunology, and Professor, Microbiology and Immunology, Uniformed Services University of the Health Sciences Events necessary in the development of Th2 immune responses are poorly understood. A popular model used to study the development of these responses involves intracutaneous inoculation with the intestinal nematode parasite Nippostrongylus brasiliensis. Using B7-1/B7-2-/- mice infected with N. brasiliensis, we have shown that Th2 effector cells are capable of developing in the absence of B7 signaling interactions, although a substantial decrease in B cell Ag-specific Ab production was observed. To examine the mechanism of T cell activation, OVA-specific DO11.10 T cells were transferred to recipient mice, which were then immunized with a combination of N. brasiliensis plus OVA or either alone. Only the combination of N. brasiliensis plus OVA triggered T cell differentiation to OVA-specific Th2 cells, suggesting that N. brasiliensis acts as an adjuvant to stimulate Ag-specific naive T cells to differentiate to effector Th2 cells. The adjuvant-like properties of N. brasiliensis suggested an innate component of the immune response may be involved in Th2 development. Using iii microarray analysis, draining ear lymph nodes from N. brasiliensis infected mice exhibited significant increases in CCL2 which is known to be involved in the recruitment of Gr-1+ neutrophils. Flow cytometric and immunofluorescent analysis of infected lymph nodes resulted in the observation of an increased presence of Gr-1+ cells. Depletion experiments, using anti-Gr-1 Ab, resulted in disruption of the polarized Th2 in vivo immune response, characterized by significantly increased levels of IFN-? gene expression, IgG2a elevations, and increased worm burden. CCL2-/- deficient mice infected with N. brasiliensis were used to determine if CCL2/CCR2 interactions were required for Gr-1 recruitment. CCL2 deficiency resulted in significantly decreased Gr-1bright cell recruitment. Absence of this population had an effect similar to that observed in anti-Gr-1 treatment experiments with increases in IFN-? and Th1 associated immunoglobulins. Flow cytometric sorting and mRNA analysis of Gr-1bright cells revealed that they consist of a purely neutrophil population which expresses high levels of TNF-? and TGF-?. These studies show the integral role that the innate immune response plays in the development of a highly polarized Th2 immune response. Overall, these studies have made significant contributions to the understanding of the development of Th2 immune responses. The adaptation of DO11.10 system into a Th2 context provides an essential tool which will allow the determination of specific factors that result in the activation of naïve T cells. As a direct result of developing this tool, we identified a neutrophil population that is essential for the proper polarization of Th2 responses. This finding is iv quite significant in that this is the first time that a neutrophil population has been implicated in the development of a Th2 immune response. While this work is still in its infancy, the work detailed in this thesis provides evidence that neutrophils may prove to be a significant target for future drug interventions in the field of allergy and asthma. v Early Events Leading to the Host Protective Th2 Immune Response to an Intestinal Nematode Parasite By John Thomas Pesce Thesis submitted to the Faculty of the Molecular and Cell Biology Program of the Uniformed Services University of the Health Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy, 2005 vi