Determination of NK cell immunophenotype and cytokine profile in patients with Rocky Mountain spotted fever

IntroductionThe intracellular pathogen Rickettsia rickettsii causes tick-borne spotted fever (also called Rocky Mountain spotted fever (RMSF) and is increasingly recognized as an emerging cause of febrile illness in Mexico. However, little is known about the early immune responses to infection. MethodologyFour RMSF pediatric patients on acute phase and eight healthy controls from Chihuahua, Mexico were recruited. The natural killer cell (NK) immunophenotype and the cytokine profile in peripheral blood were characterized by flow cytometry. ResultsThere was a decrease in total NK (CD3-CD56+) and activation receptor (CD56+NKG2D+) in NK population in patients at day 3 after hospitalization, when compared to healthy controls. Regarding to the NK cytotoxic population (CD16brightCD56dim) there was an observed decrease in patients only, between day 3 and on hospital admission. Interleukin and chemokine levels measured were significantly increased in patients upon admission compared to controls (IL-6, IL-8, IL-10, IP-10, MCP-1 and MIG). ConclusionsThis study shows that circulating NK cells are numerically decreased, while cytokines induce a pro-inflammatory process in patients.