Increased levels of interleukin-16 in the airways of tobacco smokers: relationship with peripheral blood T lymphocytes
Martti Laana, Ingemar Qvarfordtb, Gerdt C Riisea, Bengt A Anderssonc, Sven Larssona, Anders Lindéna
a Department of
Respiratory Medicine and Allergology, b Department
of Infectious Diseases, c Department of Clinical Immunology, d Göteborg
University, S-413 46 Gothenburg, Sweden
Correspondence to: Associate Professor A Lindén.
Received 18 January 1999; Returned to authors 10 March 1999; Revised version received 9 June 1999; Accepted for publication 21 June 1999
BACKGROUND
The
mechanisms behind the development of systemic immunomodulation
among tobacco smokers are not fully understood, but several studies
have indicated a role for CD8+ and/or CD4+ T cells. Interleukin (IL)-16, a cytokine released from inflammatory cells as well as bronchial epithelial cells, can recruit and activate CD4+ T cells. A
study was undertaken to establish whether the IL-16 level is increased
in the airways of tobacco smokers and to determine whether airway
levels of IL-16 are related to the number and function of systemic T lymphocytes.
METHODSBronchoalveolar
lavage (BAL) fluid was collected from eight never smokers and 18 tobacco smokers without clinical airway symptoms, and from 16 tobacco
smokers with clinical airway symptoms. Interleukin-16 protein levels in
BAL fluid were determined using enzyme-linked immunosorbent assay
(ELISA). Peripheral blood was collected for determination of CD4+ T
cell content using flow cytometry. The responsiveness of systemic
lymphocytes in smokers was assessed by measuring the proliferative
response of peripheral blood lymphocytes to the superantigen
staphylococcus enterotoxin A (SEA).
RESULTSThe IL-16
protein level in the BAL fluid was significantly higher in tobacco
smokers than in non-smokers. However, among tobacco smokers the IL-16
level was similar in asymptomatic smokers and in those with airway
symptoms. The level of IL-16 in the BAL fluid of smokers correlated
negatively with the percentage of CD4+ T cells and positively with
superantigen stimulated lymphocyte proliferation in peripheral blood.
CONCLUSIONSIn tobacco
smokers the airway IL-16 level is increased and it is possible that
this increase in IL-16 influences systemic immunomodulation by altering
the number and responsiveness of systemic T lymphocytes.
Keywords: interleukin 16; tobacco; smoking
© 1999 by Thorax
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