Lymphocyte subpopulations in pertussis

Marked increase in L-selectin-negative T cells in neonatal pertussis. The lymphocytosis explained?

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 L-selectin 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.

Aerosol infection of mice with Bordetella pertussis

Aerosol inhalation of Bordetella pertussis Tohama phase I resulted in a reproducible and uniform infection of mice (strain DDY or ICR). Mice in groups of 10 exposed for 30 min to aerosols generated from bacterial suspensions of 10(9) and 10(10) organisms per ml resulted in mean bacterial counts of 2.3 (+/- 0.3) X 10(4) and 1.0 (+/- 0.3) X 10(5) colony-forming units, respectively, in the lung of each animal. Subsequent studies using a 30-min aerosol inoculation of ICR mice with 2 X 10(9) bacterial cells per ml showed: (i) B. pertussis cells reached a maximum of about 10(7) colony-forming units per lung 14 days after inhalation. (ii) Deaths (10 to 100%, depending on mouse age) occurred 10 to 14 days after exposure. (iii) The lung weight and the leukocyte count increased from basal values of 100 mg and 10(4) leukocytes per mm3 to a plateau of 950 mg and 1.95 X 10(5) leukocytes per mm3, respectively, 14 days after challenge. (iv) There was a significantly reduced rate of body weight gain by infected mice compared to noninfected mice. (v) With mortality as the criterion for disease, susceptibility varied with the age of mice as follows: 10 days old greater than 18 greater than 28 greater than 49. (vi) Bacteria were associated with ciliated respiratory epithelial cells by scanning electron microscopy.