Expression of adhesion molecules on T lymphocytes in young children and infants--a comparative study using whole blood lysis or density gradient separation.

We investigated the use of two sample preparation techniques (whole blood lysis [WBL], and Ficoll-Hypaque density separation [FDS]) for flow cytometric estimation of adhesion molecule (CD54, CD62L and CD11b) expression on T lymphocytes from children less than 2 years old, comparing the results with normal adult controls. Using WBL methods, young children had lower percentages of CD3+/CD54+ and CD3+/CD11b+ lymphocytes, but not of CD3+/CD62L+ lymphocytes than adult controls. FDS was associated with significantly higher percentages of CD3+/CD62L+ and CD3+/CD11b+ lymphocytes in young children and adults alike, while the percentages of CD3+/CD54+ cells from adults was not affected by FDS. The percent expression of CD54, CD62L, and CD11b on T cells from both children and adults were significantly higher following FDS, with a greater increase in CD11b expression on T cells from young children, reaching adult levels. The mean fluorescence intensity (MFI) of CD62L on T cells from young children, which was lower than that of adults using WBL preparation, was significantly higher following FDS, reaching adult levels. The higher levels of adhesion molecule expression associated with FDS did not result from T-cell activation, as assessed by CD69, CD25, and HLA-DR expression. Thus, adhesion molecule expression on T lymphocytes from young children is more sensitive to modification by isolation procedures than that on adult T cells. Caution should therefore be exercised in interpreting adhesion molecule expression data on T cells from children.