Resident dendritic cells exist in various tissues. They belong to RES according to determining marks and their transitions. The main marks represent phagocytosis, fixed and mobile scavenging, endothelial and stroma-parenchyma barrier function and collagens production. Suppression of some extreme marks stimulates prevalence of remaining marks. An interesting topic concerns immune engaged dendritic cells. Their main mark is inability of transporting antigens and of presenting them to lymphatic tissue so that they start an immune reaction. Differences among dendritic cells can be detected by immunohistology. Immunopositivity of resident dendritic cells was studied in 20 tissues (lymphatic, skin, bone, soft, nervous, myocardial, lung, oesophagus, stomach, intestinal and others) by using antibodies: CD 34, F XIIIa, F VIII, actin, CD 68, S-100 protein, HLA-DR, CD3, and OPD4. Because a simple comparison of detected immunophenotypes was often ambiguous, positivity of dendritic cells was compared with positivity level of neighbouring tissues in 16 cases. Nevertheless, any single marker was not relevant in all cases. But decisive positive combinations did exist (CD 34 for non-X cells, CD 68 for phagocytes, S-100 for X cells). Dendritic cells in different and often opposite relations were found in a group of 36 cases. Diversity of tissue representation of "immunosupervising" dendritic cells reflected probably a frequence and quality of antigen stimulation in locally specific immune conditions. A surprising presence of CD 34 positive dendritic cells in border-line and stromal structures of nerves and in their tumours contributed to differential diagnosis of neurofibromas and some storiform tumours. CD 34 positivity alone does not solve problems sufficiently and applied methods will not do for determination of the share of "immunosupervising" cells in stromal reaction of malignant tumours.

Hlavův 1 patologickoanatomický ústav 1 LF UK Praha