The role of platelets in infections. I. Observations in human and murine malaria.

The interaction between platelets and microorganisms may be underestimated. Our in vivo studies support a direct role of thrombocytes in malarial infections. We have found intrathrombocytic parasites of Plasmodium vivax (in 10% of men naturally infected) and P berghei (in 53% of mice experimentally infected); these were both merozoites and trophozoites. Neither the mechanism of parasitization (whether by active penetration or by phagocytosis) nor the outcome of this phenomenon is known. However, structures suggestive of partially digested parasitic material were seen in platelets of almost 50% of the men and 75% of the mice. These findings suggest that other microoganisms (fungi, bacteria, and viruses) may also enter thrombocytes in vivo. If so, platelets could play important roles, either favorable or deleterious, in infections.