Aim: To investigate the role of accessory cells (and other chronic inflamma
tory cells) in the host immune response to testicular seminoma by defining
their immunophenotypic characteristics and topographical arrangement
Methods and results: A panel of antibodies applicable to paraffin-embedded
tissues was employed to characterize the host chronic inflammatory response
in eight cases of classical testicular seminoma. The antibodies were direc
ted against CD45RO, CD20, CD68, acid cysteine proteinase inhibitor (ACPI),
MAC387, muramidase (MUR), S100 protein, Factor XIIIa, CD21 and HLA Class IT
. In all cases the majority of the inflammatory cells were T-lymphocytes si
tuated mainly in areas of apparent tumour destruction. Large numbers of mac
rophages/dendritic cells which had not been evident by con conventional lig
ht microscopy were also demonstrated. In particular, an immunophenotypicall
y distinct population of accessory cells showing a specific pattern of dist
ribution was revealed. It clearly rimmed islands of tumour and showed stron
g positive staining for CD68, MAC387 and HLA Class II,
Conclusion: The study has identified an immunophenotypically distinct popul
ation of accessory cells showing a characteristic topographical arrangement
. It is proposed that it represents a subpopulation of macrophages which ar
e responding directly to the tumour and are likely to play a part in influe
ncing tumour dynamics.