Identifying human regulatory B cells activated by IL-4-treated mast cells or their microvesicles by mass cytometry — ASN Events
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  2. Poster Session Two
  3. Identifying human regulatory B cells activated by IL-4-treated mast cells or their microvesicles by mass cytometry

Identifying human regulatory B cells activated by IL-4-treated mast cells or their microvesicles by mass cytometry (#315)

Felix Marsh-Wakefield 1 , Angela Ferguson 1 , Helen McGuire 2 3 , Thomas Ashhurst 4 , Gary Halliday 5 , Michele Grimbaldeston 6 , Scott Byrne 1
  1. Cellular Photoimmunology Group, Infectious Diseases and Immunology, University of Sydney, Camperdown, NSW, Australia
  2. T cell Biology, Centenary Institute, Camperdown, New South Wales, Australia
  3. Ramaciotti Facility for Human Systems Biology, The University of Sydney, Sydney, New South Wales, Australia
  4. Viral Immunopathology Laboratory, Discipline of Pathology, Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia
  5. Dermatology Research Laboratories, University of Sydney, Sydney, NSW, Australia
  6. OMNI-Biomarker Development, Genentech Inc, South San Francisco, California, USA

The ultraviolet (UV) component of sunlight can protect from autoimmunity. In mice, this UV-protection is due, in part, to immune suppression via the activation of regulatory B cells. Mast cells also play an important role in UV-induced immune suppression. Because mast cells are known to influence the activation of B cells, our hypothesis is that these events are linked. Early experiments in mice demonstrated that IL-4-treated, bone marrow-derived mast cells, or their microvesicles, activated B cells that were functionally immune suppressive in vivo. These mast cell-activated regulatory B cells were phenotypically similar to those found in the lymph nodes that drain UV-exposed skin. To investigate this process in humans, mast cells derived from peripheral blood CD34+ stem cells were treated with IL-4 before being co-cultured with allogeneic B cells. There is currently no standard marker for identifying human regulatory B cells. To expand our discovery scope, we adopted a mass cytometry approach to characterise the phenotype of the B cells emerging from this co-culture. Using a combination of 35 antibodies, we could identify CD27+ memory, IgM– naïve and CD38hi IgMhi transitional B cell subsets and analyse marker expression within each group. Mast cells appeared to shift B cells towards a transitional phenotype. There were marked changes in a number of immune-related molecules, including immunoregulatory IL-10. Functional assays found these B cells in the presence of T cells increased IL-10 levels within the supernatant, although the conditions used did not suppress T cell proliferation. The large phenotypic analysis identified activation of B cells with a regulatory phenotype, whilst providing insight into how they may act based on this phenotype. By understanding how these mast cells can activate regulatory B cells, new therapeutics may be developed to target and promote this interaction as a means of treatment against autoimmune diseases.

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