Invariant Natural Killer T Cells in Bronchial Asthma

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Abstract
We have not found a remarkably high proportion of CD1d-restricted natural killer T cells (>60 percent of CD3+ cells) in bronchoalveolar-lavage specimens from patients with allergic asthma, as reported by Akbari et al. (March 16 issue).1 In five patients with allergic asthma, we found that only 0.4 to 2.1 percent of lymphocytes in bronchoalveolar-lavage fluid were natural killer T cells, on the basis of costaining with 6B11 and Vα24 antibodies (see Figure 1 of the Supplementary Appendix, available with the full text of this letter at www.nejm.org). We believe this discrepancy may result from fact that the authors did not gate using characteristic lymphocyte forward-scatter (size) and side-scatter (granularity) properties before flow analysis, consequently including large granular cells that stained nonspecifically ( Figure 1 ). A majority of CD4-staining cells in ungated bronchoalveolar-lavage specimens stain with 6B11, but only a minority of CD4+ cells within the lymphocyte gate stain with 6B11. Furthermore, since 6B11 was generated against a peptide epitope in the CDR3 region of Vα24, staining with 6B11 in the absence of Vα24 staining may indicate non–CD1d-restricted T-cell or B-cell epitopes.2-4 It is also unclear how 6B11 can stain natural killer T cells accurately if the Vα24 chain is down-regulated, as suggested by the authors. Although we observed that CD1d-restricted natural killer T cells were enriched in the bronchoalveolar-lavage specimens, as compared with peripheral blood, we did not observe a dramatic number of natural killer T cells in the bronchoalveolar-lavage fluid of our patients with asthma.