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Summary: Neutrophil recruitment from circulation to sites of inflammation is guided by multiple chemoattractant cues emanating from tissue cells, immune cells, and platelets. Here, we focus on the function of one G‐protein coupled receptor, GPR35, in neutrophil recruitment. GPR35 has been challenging to study due the description of multiple ligands and G‐protein couplings. Recently, we found that GPR35‐expressing hematopoietic cells respond to the serotonin metabolite 5‐hydroxyindoleacetic acid (5‐HIAA). We discuss distinct response profiles of GPR35 to 5‐HIAA compared to other ligands. To place the functions of 5‐HIAA in context, we summarize the actions of serotonin in vascular biology and leukocyte recruitment. Important sources of serotonin and 5‐HIAA are platelets and mast cells. We discuss the dynamics of cell migration into inflamed tissues and how multiple platelet and mast cell‐derived mediators, including 5‐HIAA, cooperate to promote neutrophil recruitment. Additional actions of GPR35 in tissue physiology are reviewed. Finally, we discuss how clinically approved drugs that modulate serotonin uptake and metabolism may influence 5‐HIAA‐GPR35 function, and we speculate about broader influences of the GPR35 ligand‐receptor system in immunity and disease. [ABSTRACT FROM AUTHOR]

Antigen presentation refers to the ability of cells to show MHC-associated determinants to T lymphocytes, leading to their activation. MHC class II molecules mainly present peptide-derived antigens that are internalized by endocytosis in antigen-presenting cells ( APCs). Here, we describe how the interface between cellular membranes and the cytoskeleton regulates the various steps that lead to the presentation of exogenous antigens on MHC class II molecules in the two main types of APCs: dendritic cells ( DCs) and B lymphocytes. This includes antigen uptake, processing, APC migration, and APC-T cell interactions. We further discuss how the interaction between APC-specific molecules and cytoskeleton elements allows the coordination of antigen presentation and cell migration in time and space. [ABSTRACT FROM AUTHOR]

Myosins comprise a family of motor proteins whose role in muscle contraction and motility in a large range of eukaryotic cells has been widely studied. Although these proteins have been characterized extensively and much is known about their function in different cellular compartments, little is known about these molecules in hematopoietic cells. Myosins expressed by cells from the immune response are involved in maintaining plasma membrane tension, moving and secreting vesicles, endo- and exocytotic processes, and promoting the adhesion and motility of cells. Herein, we summarize our current understanding of class I myosins in B cells, with an emphasis on the emerging roles of these molecular motors in immune functions. [ABSTRACT FROM AUTHOR]