1714. Revisiting the Human Neutrophil Response to Fungi from a Single-Cell Perspective
Session: Poster Abstract Session: Studies of the Interface of Host-Microbial Interaction
Saturday, October 5, 2013
Room: The Moscone Center: Poster Hall C

Background:

The rising global threat posed by fungal diseases underlines the need for a better understanding of the immune response to fungi, as well as where and why this response may fail. Human neutrophils are vital to effective anti-microbial responses, as clearly evident in the profound susceptibility of neutropenic patients to infection and the increased mortality of such patients following immunosuppression. Yet mechanistic studies of human neutrophil dynamics remain challenging, because mature neutrophils cannot be genetically manipulated or cultured.

Methods:

Tackling some of these challenges, we use innovative tools and an integrative approach to gain fresh insight into the time-dependent response of human neutrophils to encounters with fungi and surrogate models. Micromanipulation with optical tweezers and micropipettes enables us to inspect and analyze the time courses of chemotaxis, adhesion, and phagocytosis, as well as their mutual interplay, on a per-cell basis.

Results:

In this setting, the neutrophil morphology itself becomes a biosensor of chemoattractants and of target-specific microbial surface features. Integrating such single-cell experiments with flow-cytometry recognition assays, we are able to uncover and evaluate specialized functions of cell-surface receptors during contact with fungi, highlighting important receptor-ligand interactions and dispelling some misconceptions about others. We show that a strong physiological-like response of initially quiescent human neutrophils to fungal particles requires opsonization with immunoglobulins and complement. Our experiments implicate Fcγ receptors IIIB and IIA as critical fungal-recognition receptors of neutrophils, and complement receptor 3 as a major adhesion receptor sustaining cell-target attachments.

Conclusion:

Cross-talk between these receptors, and their likely stimulation by chemoattractants, exemplify a highly significant interplay of chemotaxis, adhesion, and phagocytosis. On the other hand, direct recognition of fungal surfaces by glycan receptors or Toll-like receptors appears to play a less prominent role in the initial human neutrophil phagocytic response.

huPMNvsFungi.jpg

Volkmar Heinrich, PhD and Cheng-Yuk Lee, PhD, Biomedical Engineering, University of California - Davis, Davis, CA

Disclosures:

V. Heinrich, None

C. Y. Lee, None

Findings in the abstracts are embargoed until 12:01 a.m. PST, Oct. 2nd with the exception of research findings presented at the IDWeek press conferences.