Immunophenotypic analysis and clinical significance in pediatric hemophagocytic lymphohistiocytosis.

This study characterizes changes in peripheral blood lymphocyte subsets among pediatric hemophagocytic lymphohistiocytosis (HLH) patients. Compared to healthy controls, HLH patients exhibited significantly elevated levels of CD8⁺ T cells, with concomitant reductions in B cells, CD4⁺ T cells, DPT cells, DNT cells, and the CD4⁺/CD8⁺ T cell ratio as determined by multiparametric flow cytometry. Organ dysfunction was further correlated with distinct immunophenotypic alterations. Specifically, respiratory dysfunction was associated with decreased CD4⁺ CM T cells, naïve B cells, plasmablasts, and transitional B cells; hepatic dysfunction with increased CD4⁺ Temra T cells; circulatory failure with reduced transitional B cells; and neurological dysfunction with elevated CD4⁺ Temra T cells and CD8⁺ EM T cells. Moreover, HLH patients exhibiting three or more organ dysfunctions demonstrated significantly lower levels of DPT cells, memory B cells, transitional B cells, and plasmablasts. Additionally, CD8⁺ T cells and CD8⁺ CM T cells showed positive correlations with pro-inflammatory cytokines (IL-6, TNF-α). These results suggest that depletion of CD4⁺ T cells and B cells, along with aberrant CD8⁺ T cell differentiation, may contribute to the pathogenesis of cytokine storms. These findings support dynamic monitoring of lymphocyte subsets, demonstrating potential utility for early HLH diagnosis and organ damage assessment.