In situ activation of helper T cells in the lung.
To better understand the lung and systemic responses of helper T cells mediating memory immunity to Mycobacterium tuberculosis, we used three- and four-color flow cytometry to study the surface phenotype of CD4(+) lymphocytes. Bronchoalveolar lavage (BAL) fluid and peripheral blood (PB) samples were obtained from a total of 25 subjects, including 10 tuberculosis (TB)-infected subjects, 8 purified-protein-derivative-negative subjects, and 7 purified-protein-derivative-positive subjects. In marked contrast to CD4(+) lymphocytes from PB (9% +/- 5% expressing CD45RA and CD29), the majority (55% +/- 16%) of CD4(+) lymphocytes in BAL (ALs) simultaneously expressed CD45RA, a naïve T-cell marker, and CD29, members of the very late activation family. Further evaluation revealed that CD4(+) ALs expressed both CD45RA and CD45RO, a memory T-cell marker. In addition, the proportion of CD4(+) lymphocytes expressing CD69, an early activation marker, was drastically increased in BAL fluid (83% +/- 9%) compared to PB (1% +/- 1%), whereas no significant difference was seen in the expression of CD25, the low-affinity interleukin 2 receptor (34% +/- 15% versus 40% +/- 16%). More importantly, we identified a minor population of CD69(bright) CD25(bright) CD4(+) lymphocytes in BAL (10% +/- 6%) that were consistently absent from PB (1% +/- 1%). Thus, CD4(+) lymphocytes in the lung paradoxically coexpress surface molecules characteristic of naïve and memory helper T cells as well as surface molecules commonly associated with early and late stages of activation. No difference was observed for ALs obtained from TB-infected and uninfected lung segments in this regard. It remains to be determined if these surface molecules are induced by the alveolar environment or if CD4(+) lymphocytes coexpressing this unusual combination of surface molecules are selectively recruited from the circulation. Our data suggest that ex vivo experiments on helper T-cell subsets that display distinctive phenotypes may be pivotal to studies on the human immune response to potential TB vaccines.
Raju
B
B
Division of Pulmonary and Critical Care Medicine, Department of Medicine, New York University School of Medicine, New York, New York 10016, USA.
Tung
C F
CF
Cheng
D
D
Yousefzadeh
N
N
Condos
R
R
Rom
W N
WN
Tse
D B
DB
D000328:Adult; D015703:Antigens, CD / Q000032:analysis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D001992:Bronchoalveolar Lavage Fluid; D015496:CD4-Positive T-Lymphocytes / Q000145:classification / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000145:classification / Q000276:immunology; D005260:Female; D006801:Humans; D007156:Immunologic Memory; D016130:Immunophenotyping; D019012:Integrin beta1 / Q000032:analysis; D037181:Lectins, C-Type; D017493:Leukocyte Common Antigens / Q000032:analysis; D008168:Lung / Q000166:cytology / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology*; D008297:Male; D009169:Mycobacterium tuberculosis / Q000276:immunology; D015375:Receptors, Interleukin-2 / Q000032:analysis; D006377:T-Lymphocytes, Helper-Inducer / Q000145:classification / Q000276:immunology*; D014397:Tuberculosis, Pulmonary / Q000097:blood / Q000276:immunology*; D000099192:CD69 Antigens
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D019012:Integrin beta1; D037181:Lectins, C-Type; D017493:Leukocyte Common Antigens; D015375:Receptors, Interleukin-2; D000099192:CD69 Antigens