Parasite Platelet Interactions

ABSTRACT

Platelets are not true cells. They are actually fragments of large bone marrow cells called megakaryocytes. They are small sized diskettes about 3 micro m in diameter, that on the whole amount to a mean measure of roughly 300,000 cells per micro l of blood. Individually, each features a cell of 7 fl, and a mean surface area of 8micro m2. In aggregate, blood platelets display a larger total volume and surface area than the aggregate of all other leukocyte subtypes taken together. Platelets are often classed as blood cells[1,2], and undoubtedly, play an eminent role in hemostasis and thrombosis. However, a recent research showed that platelets help to fight infections, by means that clearly exceed an exclusive function as mere players in the primary physiological processes[3]. On activation, platelets exhibit the ability to release considerable quantities of secretory products and express a multitude of immune receptors on their membrane. They are characterized by an open canalicular system, which contributes to the engulfment and/or filtration of serum components, pathogens or antigens[4]. The identification of chemokines in blood platelets has strengthened the view of these cells as participants in immune host defense. Platelet chemokines, representing pre-stored and rapidly releasable proteins, may play a major role as first-line inflammatory mediators. This is evident from their capability to recruit early inflammatory cells such as neutrophil granulocytes and monocytes and even to exhibit direct antimicrobial activity. However, insight is growing that platelet chemokines may also be long-term regulators, e.g., by activating T lymphocytes[5]. Regarding parasitic infections, blood platelets are suggested to have a role in destroying parasites. This finding may have an implication in treatment of parasites[6]. This review is an attempt to clarify the role of platelets in some parasitic infections