Extracellular traps, an ancient defense mechanism described in hemocytes of the tick Rhipicephalus microplus

NETosis is a conserved process that has been maintained throughout evolution in various species. However, in the cattle tick Rhipicephalus microplus, a process similar to NETosis, known as ETosis, has not been previously described.

In this work, we demonstrate, using fluorometry and confocal and electron microscopy, the chromatin release and the extracellular trap (ET) formation in tick hemocytes in response to various treatments.

The treatments analysis showed greater chromatin release in zymosan A-, Escherichia coli-, and LPS-treated hemocytes. This was consistent with the expression of the peroxinectin gene (pxn), the myeloperoxidase (mpo) analog gene in vertebrates, which participates in NETosis activation. Furthermore, DNA fibers were observed in tick hemocytes under all treatments, and transmission electron microscopy (TEM) showed that hemocytes treated with zymosan A have a clear nuclear envelope disruption, with a unidirectional release of chromatin.

This work investigates the existence of ETosis in tick hemocytes, representing a significant step toward understanding the tick's immune response. In addition to this contribution, new areas of research are emerging to understand the molecular mechanisms that govern this process, which we are currently exploring.