Evidence for expression of eosinophil-associated IL-12 messenger RNA and immunoreactivity in bronchial asthma.
BACKGROUND
Eosinophils are a source of cytokines within the airways of asthmatic individuals that may exert an important immunoregulatory influence.


OBJECTIVE
We examined IL-12 messenger (m)RNA and protein expression in eosinophils from peripheral blood and bronchoalveolar lavage (BAL) fluid obtained from subjects with atopic asthma (n = 7), patients with chronic bronchitis (n = 5), and nonatopic healthy control subjects (n = 7). To further define this IL-12(+) population of eosinophils for the expression of other cytokines, we colocalized IL-12 and IL-5 within the peripheral blood eosinophils.


METHODS
To detect IL-12 mRNA and protein expression, we used in situ hybridization and immunocytochemistry techniques. The double-immunocytochemistry technique was used to localize IL-12 protein to BAL eosinophils and to colocalize IL-5 and IL-12 in peripheral blood eosinophils.


RESULTS
IL-12 mRNA and immunoreactive protein were localized to peripheral blood eosinophils. BAL fluid-derived eosinophils from asthmatic subjects were also reactive to IL-12. The percentage of peripheral blood eosinophils expressing mRNA for IL-12 was significantly lower in asthmatic subjects compared with that found in eosinophils obtained from patients with chronic bronchitis (P<.001) and control patients (P <.05). Colocalization studies demonstrated that the percentages of IL-12(+) eosinophils that are also IL-5(+) were 72% in asthmatic subjects and only 11% in control subjects (P<.001).


CONCLUSIONS
These results suggest that eosinophils are a potential source of IL-12. Eosinophil-derived IL-12 may contribute and modulate the local allergic inflammatory responses.
Meakins-Christie Laboratories, and Montreal Chest Hospital, McGill University, Montreal.
E
E
Nutku
A S
AS
Gounni
R
R
Olivenstein
Q
Q
Hamid
D001249:Asthma / Q000276:immunology*; D001991:Bronchitis / Q000097:blood / Q000378:metabolism; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D002908:Chronic Disease; D004804:Eosinophils / Q000737:chemistry* / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D018664:Interleukin-12 / Q000097:blood* / Q000235:genetics* / Q000276:immunology; D015848:Interleukin-5 / Q000097:blood; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism
D015848:Interleukin-5; D012333:RNA, Messenger; D018664:Interleukin-12