For T cells positive selection takes places primary dues to the interactions with (1) and the negative selection primarily occurs dues to the interactions with (2))

1) cortical epithelial cells; (2) macrophages and dendritic cells

Explanation:

T cells, also known as T lymphocytes, are a fundamental type of cell of the immune system that determines the specificity of the immune response to specific foreign particles (antigens). T cells are produced in the Thymus (it is for that reason that they are called T cells) and then circulate throughout the bloodstream in order to recognize specific antigens in association with major histocompatibility complex (​MHC) molecules on the surface of antigen-presenting cells (APC), such as macrophages and dendritic cells. T cells undergo positive and negative selection: 1- positive T-cell selection refers to the process by which T cells bind cortical epithelial cells that express Class I or Class II MHC molecules with enough affinity to get a survival signal; whereas negative selection occurs when T cells bind to macrophages and dendritic cells that express MHC specific receptors with a strong enough affinity to get an apoptosis (programmed cell death) signal.

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