Chemokines in allergic asthma

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Journal of Clinical Investigation

Chemokines in allergic asthma

The recognition of two major classes of helper T cells, Th1 and Th2, has

focused attention on the distinctive sets of cytokines produced by these

cells and on their role in activating or suppressing inflammatory responses.

More recently, it has become clear that Th1 and Th2 cells also differ with

respect to the chemokine receptors they express, a finding that may help

explain the different timing of their entry into inflamed tissues. Now,

Panina-Bordignon and coworkers have studied the expression of chemokines and

chemokine receptors in the inflamed airways of asthmatic subjects. They find

that two Th2-restricted chemokine receptors, CCR4 and CCR8, are upregulated

in the asthmatic lung following challenge with inhaled allergens. Several

chemokines that bind CCR4 are also induced under these circumstances,

suggesting a mechanism by which Th2 cells are activated to infiltrate the

mucosa of the lung. Although the known CCR8-specific chemokines are not

induced, the authors find that the number of CCR8-positive cells correlates

with the severity of the asthmatic response, so this receptor may well be

important in this disease pathway. The induction of CCR4 and its ligands

appears to be specific for atopic disease, since a similar pattern is seen

in atopic dermatitis but not in chronic obstructive pulmonary disease, which

is thought to be driven by Th1 responses.