Subtle immunodeficiency in severe asthma: IgA and IgG2 correlate with lung function and symptoms.
BACKGROUND
Atopy, increased serum IgE and eosinophilic airway inflammation are common in asthma and may indicate aberrant immune responses, but the cause(s) are unknown. It was hypothesized that differences in serum immunoglobulins, immunoglobulin free light chains (FLC) and secretory IgA (sIgA) would exist between subjects with asthma of varying severity and normal subjects, and the levels would correlate with lung function, symptoms and airway inflammation.


METHODS
Serum IgG, IgA, IgE and IgM, IgG subclasses and FLC, and bronchoalveolar lavage sIgA were evaluated from 15 normal subjects, 9 mild and 22 severe asthmatics with similar atopic status. Asthma symptoms were obtained by questionnaire, and airway inflammation was assessed by immunostaining for five inflammatory cell types.


RESULTS
Immunoglobulin levels in all groups were generally within the normal range. However, IgA and IgG were lower in severe asthmatics than normal subjects (overall p = 0.006 and 0.02, respectively). IgA, but not IgG, correlated with lung function and asthma symptoms (r-values >0.58; p-values <0.009). Although similar among the groups, higher sIgA and IgG(2) also positively correlated with lung function and negatively with asthma symptoms (r-values >0.63; p-values <0.009). IgA and IgG/IgG(1) positively correlated with tissue mast cells.


CONCLUSIONS
Subtle alterations in IgA- and IgG(2)-mediated responses in asthma may be disease-related. As their levels are generally normal, it is possible that the quality/repertoire of immune protection provided by these isotypes, perhaps against carbohydrate epitopes, may be altered in asthma.
National Jewish Medical and Research Center, Denver, CO 80206, USA. balzars@njc.org
Silvana
S
Balzar
Matthew
M
Strand
Takanari
T
Nakano
Sally E
SE
Wenzel
D000328:Adult; D001249:Asthma / Q000097:blood / Q000276:immunology*; D001706:Biopsy; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry / Q000276:immunology; D001999:Bronchoscopy; D005260:Female; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood / Q000276:immunology; D007071:Immunoglobulin A, Secretory / Q000097:blood / Q000276:immunology; D007132:Immunoglobulin Isotypes / Q000097:blood / Q000276:immunology*; D007147:Immunoglobulin Light Chains / Q000097:blood / Q000276:immunology; D008297:Male; D008407:Mast Cells / Q000276:immunology; D008875:Middle Aged; D012129:Respiratory Function Tests; D018709:Statistics, Nonparametric
D007070:Immunoglobulin A; D007071:Immunoglobulin A, Secretory; D007132:Immunoglobulin Isotypes; D007147:Immunoglobulin Light Chains