Regulation of neutrophil-derived chemokine expression by IL-10

Regulation of neutrophil-derived chemokine expression by IL-10. Neutralizing antibodies to neutrophil chemoattractants MIP-2 or MIP-1 but not KC significantly suppressed DTH and sharply reduced neutrophil accumulation in the ear pinna. Purified bone marrow-derived neutrophils exposed to interleukin-1 (IL-1) produced chemokines in an 8-h assay. Administration of neutralizing antibody to IL-1 significantly reduced ear swelling and suppressed the levels of MIP-2, MIP-1, MIP-1, and RANTES. We conclude that neutrophils are a critical component of the DTH response to viral antigen. They are recruited to the DTH test site by Apioside MIP-2 and MIP-1, where they can be activated by IL-1. The infiltrating cells also help suppress virus replication in immunized mice. The development of an inflammatory response in herpes simplex virus type 1 (HSV-1)-sensitized hosts upon reexposure to viral antigen has been known for decades (25, 32). However, the mechanism accounting for this immunologically specific response, delayed-type hypersensitivity (DTH), is quite complex, and identification of the cellular and molecular events inherent in this phenomenon remains incomplete. A clearer understanding of the DTH mechanism is pertinent because it represents a form of cell-mediated immunity and, as such, has the potential to provide protection against the virus or, alternatively, contribute to the pathogenesis of herpesvirus-induced disease (31). DTH can be elicited by inoculation of virus antigen into the ear pinna (46) of the HSV-1-infected mouse. Optimal responsiveness occurs 6 to 9 days postinfection and has been shown via adoptive transfer studies and cell depletion experiments to be mediated by the CD4 Apioside T-cell subset (21, 38, 39). Although neutrophil influx after HSV-1 ocular infection is well documented (36, 37, 53), the accumulation of neutrophils in the skin, i.e., at the DTH test site, was not initially appreciated. Traditionally, neutrophils have been thought to function only as phagocytic effector cells. More recently, however, it has become evident that neutrophils can express a variety of immunoregulatory molecules (6, 34), and thus may participate more actively in DTH. The identification of chemotactic factors involved in the recruitment of neutrophils to sites of DTH responsiveness also is incompletely defined. Chemokines are logical candidates (45, 60). They constitute a growing Apioside E2F1 family of low-molecular-weight secreted proteins that can chemoattract leukocyte subpopulations from the blood to sites Apioside of inflammation, including DTH. Chemokines induce cell activation and migration by binding to specific G protein-coupled receptors expressed on the surface of leukocytes. In the mouse, two important neutrophil chemoattractants are macrophage inflammatory protein-2 (MIP-2) and KC (40, 55). These C-X-C chemokines are known to induce potent chemotaxis of the neutrophil in vitro, and injection of these chemokines either subcutaneously or intracorneally in mice results in a predominant neutrophil influx (15, 40, 49, 55, 58). Furthermore, these chemokines are found at the site of HSV-1 infection (58), and antibody neutralization of endogenous MIP-2 can alter the host Apioside response in models of both viral (58) and bacterial (18, 27, 47) infection. MIP-1 is a member of the C-C chemokine supergene family (45, 60). Like other members of this family, MIP-1 is chemotactic for mononuclear phagocytes and lymphocytes (44, 48). However, MIP-1 has also been reported to be chemotactic for neutrophils both in vivo and in vitro (1, 16). Experiments with mice carrying a disrupted MIP-1 gene (9, 51) or animals given antibody to neutralize endogenous MIP-1 (1, 22, 52) have revealed its importance for cellular recruitment in the expression phase of cell-mediated immunity, including that in HSV-1 infection (51, 52). The focus of the present investigation was to evaluate the contribution of neutrophils in the DTH response to HSV-1 antigen and to identify mediators that affect the recruitment of these cells to the site of virus antigen deposition. We also investigated whether the recruited neutrophils helped to limit virus replication in immunized hosts. MATERIALS AND METHODS Animals. Four-week-old female BALB/c mice were obtained from Charles River Laboratories (Wilmington, Mass.). Animals were cared for in compliance with federal, state, and local regulations. Antibodies and reagents. The rat hybridoma RB6-8C5, which produces anti-mouse granulocyte monoclonal antibody (MAb), was a gift from R. Coffman (DNAX Research Institute, Palo Alto, Calif.). This antibody was prepared as.