Chemokine receptor expression on allergen-specific T cells in asthma and allergic bronchopulmonary aspergillosis.

BACKGROUND: Allergic bronchopulmonary aspergillosis (ABPA) is a rare variant of severe asthma resulting from hypersensitivity to Aspergillus fumigatus (Asp f) present in the airways. AIMS OF THE STUDY: We analyzed the expression of a panel of six chemokine receptors (CCR3, CCR4, CCR8, CCR5, CXCR3 and CXCR4) on total blood CD4(+) T cells and Asp f-specific-T cells in ABPA patients. We hypothesized that chemokine receptor pattern on T cells differs between ABPA patients, non-ABPA allergic asthmatics sensitized to Dermatophagoides pteronyssinus (Der p) or Phleum pratense (Phl p) and healthy controls.
METHODS: We used the fluorescent dye PKH26, a membrane bound marker, to identify accumulated proliferating (cell-sorted PKH26(low)) CD4(+) T cells in response to allergens (Asp f, Der p, Phl p) or recall antigens (PPD and TT). Chemokine receptor expression was analyzed by flow cytometry on proliferating CD3(+) CD4(+) PKH26(low) cells.
RESULTS: Stimulation of CD4(+) T cells with the relevant allergen resulted in different patterns of chemokine receptor expression in ABPA and non-ABPA allergic asthmatics. Upon Asp f exposure, proliferating CD4(+) T cells from ABPA patients down-regulated the expression of CCR4 and CXCR3 while CCR4 and CXCR3 were up-regulated in allergen-specific T cells from non-ABPA allergic asthmatics. Considering each group of patients, the pattern of chemokine receptors expressed on proliferating allergen-specific CD4(+) T cells was similar to that expressed by recall antigen-specific T cells.
CONCLUSIONS: The down-regulation of CCR4 and CXCR3 after allergen exposure in Asp f-specific T cells seems to be a characteristic feature of ABPA patients and requires further evaluation.