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Marked Increase in L-Selectin–Negative T Cells in Neonatal Pertussis
The Lymphocytosis Explained?

S. David Hudnall MD, Claudia P. Molina MD
DOI: http://dx.doi.org/10.1309/BANX-8JKM-TUQN-4D6P 35-40 First published online: 1 July 2000


The detailed immunophenotype of peripheral blood lymphocytes from a neonate with pertussis was determined by flow cytometry and compared with results from cord blood from healthy newborns. Most (72%) of the lymphocytes were CD3+ T cells with a normal CD4/CD8 ratio (2.5). The T cells were largely HLA-DR negative and CD45RA+, consistent with unstimulated naïve T cells. Almost all of the CD4+ T cells were Leu8 (L-selectin, CD62L) negative, while almost all of the CD8+ T cells were CD28+. There was no increase in CD7– CD4+ T cells (Th2-like). No relative increase in CD16/56+ NK cells (5%) or CD19/20+ B cells was seen. The most dramatic finding in this case was the remarkable lack of expression of Lselectin by the T cells. L-selectin expression is associated with homing of peripheral blood lymphocytes to lymph nodes. The dramatic reduction in L-selectin expression of the T lymphocytes in pertussis, perhaps induced by pertussis toxin, likely prevents homing of the T cells to peripheral lymphoid tissues and provides a likely explanation for the marked lymphocytosis noted in this disease.

Key Words:
  • Pertussis
  • Whooping cough
  • Lymphocytosis
  • Immunophenotype
  • L-selectin
  • T-cell subsets
  • Flow cytometry
  • CD62L
  • Leu 8