β2 integrins are of critical importance for leukocyte extravasation through vascular endothelia and for T cell activation. To elucidate the role of β2 integrins in T cell–mediated immune responses, allergic contact dermatitis (ACD), irritant dermatitis, and delayed-type hypersensitivity (DTH) were assessed in mice lacking the β2 integrin subunit, CD18. ACD and DTH responses, but not edema formation, were severely suppressed in CD18–/– mice. Extravasation of CD18–/– T cells into eczematous skin lesions was greatly impaired, whereas migration of Langerhans cell precursors and dendritic cells was normal in CD18–/– mice. CD18–/–lymph nodes (LNs) contained an abnormal population of CD3–CD44high lymphocytes and showed evidence of widespread T cell activation. T cells from regional LNs of sensitized CD18–/– mice proliferated in response to hapten challenge, and subcutaneous injection of sensitized syngeneic LN cells directly into ears of hapten-challenged naive recipients restored the defective ACD in CD18–/– mice, suggesting that CD18 is not required for priming of naive T cells but is indispensable for T cell extravasation. Thus, a dysfunction of T cells, in addition to granulocytes, may contribute to the pathophysiology of leukocyte adhesion deficiency type I, which arises from mutations in the human CD18 gene.
Stephan Grabbe, Georg Varga, Stefan Beissert, Meike Steinert, Gunther Pendl, Stephan Seeliger, Wilhelm Bloch, Thorsten Peters, Thomas Schwarz, Cord Sunderkötter, Karin Scharffetter-Kochanek
Guidelines: The Editorial Board will only consider letters that we deem relevant and of interest to our readers. We will not post data that have not been subjected to peer review, nor will we post letters that are essentially a reiteration of another letter. We reserve the right to edit any letter for length, content, and clarity. Authors will be notified by e-mail if their letters were accepted. No appeals will be considered.
Specific requirements: All letters must be 400 words or fewer. You may enter the letter as plain text or HTML. The author's name and e-mail address are required, and will be posted with the letter. All possible conflicts of interest must be noted, even if they are not posted. If you wish to include a figure (keep in mind that non-peer-reviewed data will not be posted), please contact the editors directly at email@example.com.