Human Neutrophil-Expressed CD28 Interacts with Macrophage B7 to Induce Phosphatidylinositol 3-Kinase-Dependent IFN-γ Secretion and Restriction of Leishmania Growth

Abstract

We previously showed that CD28 is expressed on human peripheral blood neutrophils and plays an important role in CXCR-1 expression and IL-8-induced neutrophil migration. In this work we demonstrate that Leishmania major infection of macrophages results in parasite dose-dependent IL-8 secretion in vitro and in IL-8-directed neutrophil migration, as blocked by both anti-IL-8 and anti-IL-8R Abs, toward the L. major-infected macrophages. In the neutrophil-macrophage cocultures, both CTLA4-Ig, a fusion protein that blocks CD28-CD80/CD86 interaction, and a neutralizing anti-IFN-γ Ab inhibit the anti-leishmanial function of neutrophils, suggesting that the neutrophil-macrophage interaction via CD28-CD80/CD86 plays an important role in the IFN-γ-dependent restriction of the parasite growth. Cross-linking of neutrophil-expressed CD28 by monoclonal anti-CD28 Ab or B7.1-Ig or B7.2-Ig results in phosphatidylinositol 3-kinase association with CD28 and in wortmannin-sensitive but cyclosporin A-resistant induction and secretion of IFN-γ. Whereas the neutrophils secrete IFN-γ with CD28 signal alone, the T cells do not secrete the cytokine in detectable amounts with the same signal. Thus, neutrophil-expressed CD28 modulates not only the granulocyte migration but also induction and secretion of IFN-γ at the site of infection where it migrates from the circulation.

Cutting Edge: Neutrophil Granulocyte Serves as a Vector forLeishmaniaEntry into Macrophages

“…4 Using an end-point titration assay, we could demonstrate that the number of viable Leishmania remained stable inside PMN 18 and 42 h after infection (62.1 Ϯ 3.1 and 59.3 Ϯ 2.9 Leishmania per 1000 PMN, respectively, n ϭ 4). Although these findings appear to contradict some earlier reports indicating that the PMN exert antileishmanial activity (10,11), the data confirm other studies describing the diseasepromoting effect of PMN in Leishmania infection (12,13). Importantly, our data are in line with the recent observation that apoptotic PMN exacerbate Leishmania infection (14).…”

Polymorphonuclear neutrophils deliver activation signals and antigenic molecules to dendritic cells: a new link between leukocytes upstream of T lymphocytes

“…ϩ PMNs have been shown to activate Leishmania-infected macrophages to produce IFN-␥ via the CD28-CD80/CD86 pathway [24]. As a result of the lack of CD28 expression on PMNs before and during coculture with DCs, this pathway cannot be involved in the interactions reported here.…”

“…3A), an usually T lymphocyte-associated costimulatory molecule, which has been shown to be expressed on a PMN subset [24]. The proportion of dead or apoptotic PMNs was similar in control and cocultured PMNs (Fig.…”

“…Cell-surface, molecule-dependent interactions between PMNs and other myeloid cells have already been reported [24,41,42]. CD28…”

Neutrophils and Macrophages Cooperate in Host Resistance againstLeishmania braziliensisInfection

“…Nonetheless, other mechanisms of cross-talk between infected macrophages and neutrophils have been described previously, such as the transfer of lactoferrin (41) and myeloperoxidase (42) and, more recently, the presence of neutrophil granules that colocalized with intracellular mycobacteria (43). It was also shown that the CD28/ CD80-CD86 interaction on neutrophil/macrophages induces IFN-␥ production, restricting the growth of L. major (44). Importantly, the mechanisms leading to cure and resistance to Leishmania infection are associated with macrophage activation, resulting from TNF-␣-and IFN-␥-induced production of free radicals and ultimately with destruction of the intracellular parasites (45,46).…”