Correspondence
Invariant Natural Killer T Cells in Obstructive Pulmonary Diseases
N Engl J Med 2007; 357:193-195July 12, 2007
- Article
To the Editor:
Vijayanand et al. (April 5 issue)1 show that fewer than 2% of the T cells from the airways of patients with asthma were invariant natural killer T cells. It is surprising that the authors consider this finding to be normal, since the frequency of invariant natural killer T cells in the peripheral blood and lungs of subjects without asthma has been reported to be much lower (see additional comments in the Supplementary Appendix, which is available with the full text of this letter at www.nejm.org). In addition, the results of six other studies differ from those of Vijayanand et al. and instead show an enrichment of invariant natural killer T cells in the lungs of patients with asthma.2-5
Notably, the conclusions of Vijayanand et al. might have been quite different if they had analyzed cells obtained from bronchoalveolar-lavage fluid, and not just from sputum, of subjects without asthma. Moreover, the number of invariant natural killer T cells in airways of patients with asthma, as reported by Vijayanand et al., may be low, since their methods to minimize false positives may have diminished the sensitivity of their assays.
Finally, the number of invariant natural killer T cells in the lungs of patients with asthma is likely to be highly variable. Our recent studies indicate that this number ranges from 1 to 63% of CD3+ cells, which roughly correlates with control of asthma symptoms. The important issue now is not determining whether invariant natural killer T cells are present in the lungs of patients with asthma but, rather, understanding the mechanisms that control the frequency of invariant natural killer T cells in the lungs and how even small numbers of such cells in the lungs can trigger asthma symptoms.
5 ReferencesOmid Akbari, Ph.D.
Harvard Medical School, Boston, MA 02115John L. Faul, M.D.
Connolly Hospital, Dublin 15, IrelandDale T. Umetsu, M.D., Ph.D.
Harvard Medical School, Boston, MA 02115
dale.umetsu@childrens. harvard. edu 1
Vijayanand P ,Seumois G ,Pickard C , et al. Invariant natural killer T cells in asthma and chronic obstructive pulmonary disease. N Engl J Med 2007;356:1410-1422
Full Text | Web of Science | Medline2
Invariant natural killer T cells in bronchial asthma. N Engl J Med 2006;354:2613-2616
Full Text | Web of Science | Medline3
Spinozzi F ,Porcelli SA . Recognition of lipids from pollens by CD1-restricted T cells. Immunol Allergy Clin North Am 2007;27:79-92
CrossRef | Web of Science | Medline4
Sen Y ,Yongyi B ,Yuling H , et al. V alpha 24-invariant NKT cells from patients with allergic asthma express CCR9 at high frequency and induce Th2 bias of CD3+ T cells upon CD226 engagement. J Immunol 2005;175:4914-4926
Web of Science | Medline5
Akbari O ,Faul JL ,Hoyte EG , et al. CD4+ invariant T-cell-receptor+ natural killer T cells in bronchial asthma. N Engl J Med 2006;354:1117-1129
Full Text | Web of Science | Medline
To the Editor:
The findings of Vijayanand et al., who detected low numbers of invariant natural killer T cells in the airways of patients with mild or moderate asthma, contrast with the results of a study by Akbari et al.1 We were unable to demonstrate the presence of invariant natural killer T cells (<1% of T cells) in bronchoalveolar-lavage fluid from six patients with mild asthma. In addition, we were unable to detect an influx of invariant natural killer T cells into the airways after segmental allergen challenge. However, with the use of an antibody specific to invariant natural killer T cells (clone 6B11), we did detect a clear but small population of invariant natural killer T cells in peripheral blood from the patients with asthma (0.04 to 0.50% of all T cells), which confirms that this antibody is indeed functional. Thus, our results support the findings of Vijayanand et al., who did not detect invariant natural killer T cells in bronchoalveolar-lavage fluid obtained from most patients with asthma.
1 ReferencesKai Bratke, Ph.D.
Peter Julius, M.D.
J. Christian Virchow, M.D.
University Medical Clinic Rostock, 18057 Rostock, Germany
kabratke@med.uni-rostock. de 1
Akbari O ,Faul JL ,Hoyte EG , et al. CD4+ invariant T-cell-receptor+ natural killer T cells in bronchial asthma. N Engl J Med 2006;354:1117-1129
Full Text | Web of Science | Medline
To the Editor:
Vijayanand et al. provide no data on bronchoalveolar-lavage analysis in healthy controls. Recently, we examined blood and bronchoalveolar-lavage samples from 16 healthy subjects, using Vα24 and Vβ11 monoclonal antibodies. Invariant natural killer T cells constituted less than 1% of the CD3+ cells, partly expressing natural killer–cell marker CD56 (Table 1Table 1
Invariant Natural Killer T Cells in Specimens from 16 Healthy Subjects.). We found no compartmentalization of invariant natural killer T cells, which is consistent with the findings of Vijayanand et al.Michiel Heron, M.Sc.
Anke M.E. Claessen, Ph.D.
Jan C. Grutters, M.D., Ph.D.
St. Antonius Hospital, 3435 CM Nieuwegein, the Netherlands
m.heron@antonius. net Author/Editor Response
In our article, we state that less than 2% of airway T cells are invariant natural killer T cells, yet in many of the patients with asthma, less than 1% of airway T cells were invariant natural killer T cells, and in six of eight patients with moderate asthma, no such cells were detected at all. Thus, it is not surprising that polymerase-chain-reaction assays for detecting Vα24 and Vβ11 domains of the T-cell receptor were also negative in patients who had no invariant natural killer T cells and in the one patient who had 0.2%.
Bratke et al., Mutalithas et al.,1 and Thomas et al.2 found similarly low invariant natural killer T-cell counts. Although we did not analyze invariant natural killer T cells in bronchoalveolar-lavage samples from healthy subjects, Heron et al. report counts that were also less than 1%. Bratke et al. also report finding no influx of invariant natural killer T cells after allergen challenge. Thus, Akbari et al. are the only correspondents who have found that invariant natural killer T cells are a large proportion of airway T cells in patients with asthma.
It would be very helpful if Akbari et al. would provide full details of their gating strategy, showing that cells they believe to be invariant natural killer T cells back-gate into the lymphocyte population on the forward and side scatter plot. In our article, we provided such data. This information would allow other researchers to compare our methods and results with those of Akbari et al. We are concerned that the high invariant natural killer T-cell counts found by Akbari et al. may be due to nonspecific binding of antibodies to Fcγ receptors on macrophages, given the fact that they applied only 2% fetal-calf serum to samples from most patients and polyclonal IgG to samples from three patients — both of which are suboptimal methods. In our article, we provide details of all the appropriate controls to show that there is no question of loss of invariant natural killer T cells because of exclusion of doublets and dead cells. Checking for viability by means of trypan blue staining is insufficient for flow cytometry, since this method does not detect cellular debris consisting of DNA, which binds antibodies nonspecifically. This factor is particularly important in a disease such as asthma, in which epithelial shedding and an increased turnover of inflammatory cells result in abundant debris.
We do not dispute a role of invariant natural killer T cells in asthma, although it is worth noting that recent articles question the pathological significance of these cells, even in animal models.3 Overall, the attention given to invariant natural killer T cells in asthma has to be viewed in the context of an increasing number of negative studies.
3 ReferencesPandurangan Vijayanand, M.D.
Gregory Seumois, M.Sc.
Ratko Djukanovic, M.D.
University of Southampton, Southampton SO16 6YD, United Kingdom
vijay@soton.ac. uk 1
Mutalithas K ,Croudace J ,Guillen C , et al. Bronchoalveolar lavage invariant natural killer T cells are not increased in asthma. J Allergy Clin Immunol 2007;119:1274-1276
CrossRef | Web of Science | Medline2
Thomas SY ,Lilly CM ,Luster AD . Invariant natural killer T cells in bronchial asthma. N Engl J Med 2006;354:2613-2615
Full Text | Web of Science | Medline3
Das J ,Eynott P ,Jupp R , et al. Natural killer T cells and CD8+ T cells are dispensable for T cell-dependent allergic airway inflammation. Nat Med 2006;12:1345-1346
CrossRef | Web of Science | Medline
- Citing Articles (2)
Citing Articles
