Immune cell infiltration of intrinsic and metastatic intracranial tumours

Immune escape is one prerequisite for the formation of neoplasms that is reflected by the pattern of immune cell infiltration. Abundant monocytic infiltration without apparent phagocytic activity is well known in human gliomas, while other types of human intracranial tumours have not yet been investigated.

We analysed LCA-positive lymphocytes and CD68-positive macrophages/microglia by immunohistochemistry in 67 intracranial neoplasms: 18 glioblastomas (GBM), 14 primitive neuroectodermal tumours and medulloblastomas (PNET), metastases of 9 adenocarcinomas and of 8 malignant melanomas, and 18 benign meningiomas.

Levels of monocytic infiltration in GBM and adenocarcinomas were higher than in PNET and meningiomas. Lymphocytes were rare in all tested tumours. No differences were found between all malignant neoplasms and benign meningiomas and between primary intracranial and metastatic tumours.

Malignancy or primary intracranial origin seem not to be major determinants of immune cell infiltration. Different patterns of cytokine production may explain the differences in single tumour entities.