Immune cells infiltrate tumors and make up a significant component of the multicellular cancer microenvironment, yet the immune system often fails to prevent tumor formation and progression. One explanation for this paradox is the presence of tolerance-promoting regulatory T cells (Tregs). Tregs were known to be essential for maintaining self-tolerance. Tregs have been found to promote tolerance to tumors in mouse models. Treg infiltration in human tumors and malignant ascites is associated with worse clinical outcomes for various types of cancers.

Lymphomas are tumors of the lymphatic system, but its cells, mainly lymphocytes constitute morphological substrate of the immune system. Lymphocytes are characterized by the expression of several antigens manifested in subsequent stages of development. These, so called differentiation antigens grouped in CD classification are also expressed in lymphomas. They may be traced by means of various methods, and in particular, by flow cytometry.

Blood cells are exposed to any agent absorbed or injected into the bloodstream, even those rapidly metabolised and extracted. Although anucleated, blood platelets are highly organized cells, rich in different types of organelles. They respond to small amounts of circulating molecules by secreting a number of active compounds stored in specific granules. That«s the reason blood platelets are used as pharmacological model for new drugs evaluation for many years.