Expression of HLA Class I and II (DR, DP and DQ) Determinants in Fetal and Postnatal Salivary Glands

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Abstract
Fetal (n=20)and postnatal (n = 40) parotid glands were examined by two‐colour immunohisto‐chemistry combining monoclonal and polyclonal antibody reagents lo study the expression of HLA class I and Il (DR. DP. and DQ). CD45 and CD3, The epithelium lacked class II during fetal life, whereas class I determinants appeared in some acini and most major ducts. Fetal vessels were positive for both class I and class II (mainly DR), suggesting constructive expression. Some class II‐positive (DR > DP DQ) histiocytic cells, scaltered CD45+ leucocytes, and very few CD3+ T cells were present in the fetal stroma. The epithelium remained DR‐negative the first few weeks after birth, but brisk expression was seen subsequently, DP and DQ remained virtually negative in the epithelium throughout the first year. A slight postnatal increase of class II expression (DR > DP > DQ). along with an apparent decrease in class I. was observed in the endothelium. The number of class Il‐positive histiocytic cells. CD45+ leucocytes and CD3+ T cells, as well as the proportion of presumably activated (DR+) T cells, increased a few weeks after birth. The local immune system hence seemed to be stimulated by extrinsic factors, but the overall number of T cells nevertheless remained small. Stimuli other than T cell‐derived lymphokines, therefore, probably explained the brisk postnatal epithelial DR induction.