Lymphopenic community-acquired pneumonia is associated with a dysregulated immune response and increased severity and mortality.

OBJECTIVES

Lymphopenic (<724 lymphocytes/µL) community-acquired pneumonia (L-CAP) is an immunophenotype with an increased risk of mortality. We aimed to characterize the l-CAP immunophenotype though lymphocyte subsets and the inflammatory response and its relationship with severity at presentation and outcome.

METHODS

Prospective study of 217 immunocompetent patients hospitalized for CAP. Lymphocyte subsets (CD4, CD8, CD19, and natural killer [NK] cells) and inflammatory cytokines were analyzed on days 1 and 4, and immunoglobulin subclasses were analyzed on day 1 in a nested group.

RESULTS

39% of patients showed l-CAP, with decreased levels of all lymphocyte subsets with a partial recovery of CD4 and CD8 cells by day 4. l-CAP patients exhibited higher initial severity and systemic levels of interleukin (IL)-8, IL-10, granulocyte colony-stimulating factor, and monocyte chemoattractant protein-1. Initial IgG2 levels were lower in patients with <724 lymphocytes/µL and positively correlated with ALC, CD4, and CD19 cell counts. Low CD4 counts (<129 cells/µL) also independently predicted 30-day mortality after adjusting for age, gender, and the CURB-65 score.

CONCLUSIONS

l-CAP is characterized by CD4 depletion, a higher inflammatory response, and low IgG2 levels that correlated with greater severity at presentation and worse prognosis. l-CAP is an immunophenotype useful for rapidly recognizing severity.