Abstract: Objective To explore the abnormal expression of CD4+ T cells and NK cell perforin（PRF）to evaluate the immune status and condition of children with hand ⁃foot ⁃mouth disease（HFMD），and to analyze its guiding value for clinical prognosis. Methods A total of 143 children with HFMD admitted to our hospital from January 2017 to June 2020 were selected and divided into normal group（n = 67），severe group（n = 45）and critical group（n = 31）. Another 35 children with normal findings in physical examination were selected as the control group. T lymphocyte subsets（CD3+T，CD4+T，CD8+T），monocytes（CD14+ ），NK cell PRF，and granzyme B（GrzB），B cell subsets（CD19 + ），immunoglobulins（IgA，IgG，IgM）and complement（C3，C4）levels were compared. The expression of CD4+ T cells，NK cells PRF and the severity of the disease（PCIS score，PRISM III score）as well as the prognostic relationship were analyzed. Results The numbers of CD3 +T，CD4 +T，CD14 +， CD19+B，and NK cells in the severe group，critical group，and normal group were lower than those in the control group. The expressions of NK cell PRF and GrzB were higher than those in the control group where the severe group and the critical group had more obvious changes than the normal group（P < 0.05）. The levels of IgA，IgG，IgM and complement C3 and C4 in each group have no significant difference（P > 0.05）；Pearson correlation analysis showed that CD4+ T cells were positively correlated with PCIS score（r = 0.665，P < 0.05），and negatively correlated with PRISMⅢscore（r = -0.757，P < 0.05），PRF was negatively correlated with PCIS score（r = -0.615，P < 0.05）， and positively correlated with PRISMⅢ score（r = 0.596，P < 0.05）. CD4+ T cells in children with good prognosis were higher than those with poor prognosis，and PRF of NK cells was lower than those with poor prognosis（P < 0.05）. Conclusion Children with hand，foot and mouth disease had obvious low expression of CD4+ T cells and high expression of NK cells PRF，both of which could be used to assess the cellular immune status of severely ill children and are related to the severity of the disease and poor prognosis.

Key words:

CD4+ T cells； NK cell perforin； hand, foot and mouth disease； immune function； en? terovirus 71； prognosis