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New attractants of T lymphocytes and several activation factors contribute to inflammation in vernal keratoconjunctivitis (VKC), a molecular study has found. The findings may help to explain how T lymphocytes are recruited to the conjunctiva.
Three chemokines—pulmonary and activation regulated chemokine (PARC), macrophage derived chemokine (MDC), and 1-309, the MDC receptor CCR4—strongly attractive to T lymphocytes were present in the cytoplasm of inflammatory cells in sections of conjunctivas from patients with VKC. PARC predominated, appearing in all specimens and in many more of the abundant CD3+ T lymphocytes in the upper substantia propria. MDC and 1-309 showed up in nine and six specimens, respectively.
Among five activation factors tested, CD25 occurred in significantly more T lymphocytes than the others. The mean cell numbers for the remaining factors were significantly different from each other and were, in descending order, CD26, CD62L, CD71, and CD30. CD25 also showed a strong link with CD3+ T lymphocytes and with the number of cells expressing PARC. Conjunctivas from controls with no inflammation were weakly positive only for CD26.
Biopsy specimens of limbal conjunctiva were taken from 11 Saudi children with active disease and eight control children of similar age having an operation for strabismus. Thin sections were stained immunohistochemically for each chemokine and activation factor.
How and why T lymphocytes present in this chronic inflammatory condition migrate to the conjunctiva is not understood. So the new chemokines were prime candidates for study.