Eosinophil as antigen‐presenting cell: activation of T cell clones and T cell hybridoma by eosinophils after antigen processing

Abstract

We have studied the role of murine eosinophils as antigen-presenting cells (APC). Eosinophils have several characteristics that support the hypothesis of its function as potential APC: they have phagocytic capacity, express adhesion molecules and major histocompatibility complex (MHC) class II antigens and can produce and release interleukin-1 (IL-1). We have obtained several T cell clones specific for Mesocestoides corti antigens and used T cell hybridoma specific for ovalbumin (OVA) to test this hypothesis. Granulocyte-macrophage colony-stimulating factor-activated pure eosinophils (99.9%), express class II antigens and are able to present M. corti antigens to specific T cell clones or OVA to T cell hybridoma 3DO 11.10, inducing the proliferation of T cell clones and IL-2 release by the T cell hybridoma. Proliferation of T cells clones is dependent on the number of eosinophils used as APC. We have compared the efficiency of the same number of macrophages and eosinophils as APC, and have found that macrophages are more efficient than eosinophils. Lysosomotropic agents, such as chloroquine and ammonium chloride, that inhibit antigen processing, impaired eosinophil presentation. This presentation is restricted by MHC class II and inhibited by anti-I-Ad monoclonal antibody. The present study provides clear evidence of APC function for eosinophils. Our investigation points to a new role for eosinophils in the immune response.

Eokines: synthesis, storage and release from human eosinophils

“…Stored cytokines in eosinophils may serve as a rapidly mobilizable reservoir of inflammatory mediators in allergic reactions association with eosinophils, in contrast to T cells and other cells which do not store these compounds. The expression of these molecules by eosinophils suggest that these cells may play an afferent role in the immune system, since eosinophils can express MHC Class II and present antigen to T cells (Del Pozo et al 1992) and produce IL-4 upon activation , Nonaka et al 1995. It is likely that the actions of many eosinophil-derived cytokines are mediated by putative paracrine, autocrine, or juxtacrine signalling mechanisms, since the quantities of cytokines released are low in comparison to levels achieved by in vitro stimulation of T cells.…”

Peripheral eosinophil count both before and after liver transplantation predicts acute cellular rejection

“…Finally, Weller recently pointed out new functional capabilities of eosinophils apart from those of an end-stage effector cell. 31 Following reports on HLA-DR expression of eosinophils recovered from the sputum 32 and the airways 33 of asthmatic patients and the peritoneal cavity of pediatric dialysis patients, 34 he and the group of Del Pozo 35 demonstrated the ability of eosinophils to function as HLA-DR-dependent, MHC-restricted, antigenpresenting cells in stimulating T lymphocyte responses in vitro. These observations may well be of relevance to the role of eosinophils in the development of ACR.…”

Thymic Indoleamine 2,3-Dioxygenase-Positive Eosinophils in Young Children

“…Over the last few years, a new paradigm has emerged describing eosinophils as significant contributors to both localized innate and acquired immunity associated with Th1 and Th2 immune profiles and systemic adaptive responses. 6 Eosinophils were recently shown to act as antigen-presenting cells since they express several important co-stimulatory molecules, 7 further supporting the notion of their modulatory role in adaptive immune responses. Eosinophils home naturally to the thymus in neonates in the absence of any detectable "danger signal" 8 and data from mice suggest that thymic eosinophils (along with thymic dendritic cells) may be involved in the education of thymocytes.…”

“…22 Eosinophils are considered as terminal effectors of allergic responses in asthma and other inflammatory conditions, including inflammatory responses in favor of the host against parasitic helminth infections. 23 These cells also have the capacity to interact with T cells, present antigen, and promote Th2 polarization, 7,24 and thereby modulating adaptive immune responses. Although the presence of eosinophils in the human thymus has previously been described, 8,[25][26][27][28] their ontogeny and immunomodulatory role in the thymic microenvironment is unclear.…”