From Classical to Unconventional: The Immune Receptors Facilitating Platelet Responses to Infection and Inflammation

SIMPLE SUMMARY: Platelets are small and numerous cells, second only to red blood cells in the bloodstream. They have been recognized mainly for their contributions to blood clotting, however, we now know that they also play important roles in our responses to infection and inflammation. In this extensive review, we cover the “classic” platelet receptors involved in blood clotting and “unconventional” immune receptors that platelets possess and how both groups contribute to our immune responses. Platelet receptors can interact with bacteria and affect the behaviors of white blood cells which fight infection. Additionally, these receptors can be involved in autoimmune conditions, when the body mounts an immune response against itself. Continued research on these interactions could lead to development of new treatments against numerous diseases. ABSTRACT: Platelets have long been recognized for their role in maintaining the balance between hemostasis and thrombosis. While their contributions to blood clotting have been well established, it has been increasingly evident that their roles extend to both innate and adaptive immune functions during infection and inflammation. In this comprehensive review, we describe the various ways in which platelets interact with different microbes and elicit immune responses either directly, or through modulation of leukocyte behaviors.