part of part of lacks_plasma_membrane_part has plasma membrane part develops from immature alpha-beta T cell double-positive, alpha-beta thymocyte CD4-positive, alpha-beta thymocyte SP CD4 cell CD4-positive, alpha-beta immature T-lymphocyte CD4-positive, alpha-beta immature T-cell An immature alpha-beta T cell that is located in the thymus and is CD4-positive and CD8-negative. https://cellxgene.cziscience.com/cellguide/CL_0000810 CD4-positive, alpha-beta thymocytes are a subset of newly developed T cells found within the thymus. This cell type is characterized by the expression of the surface proteins CD4 and T-cell receptor alpha-beta (TCR αβ). T-cell receptors are integral to the function of the T cell, allowing it to recognize and bind to specific antigens presented by other cells, while expression of the CD4 TCR coreceptor designates them as precursors to helper T cells. These cells represent a late stage in T cell development. Progenitor cells reach the thymus, the site of T cell maturation, and begin as double negative (DP) cells that express neither CD4 nor CD8. The cells then become double positive (DP), expressing both CD4 and CD8. The cells undergo negative and positive selection processes, in which cells are removed if they bind too strongly to self-major histocompatibility complex (MHC) molecules presenting self-peptide and cells are given survival signals if they bind weakly to self-MHC, respectively. This ensures that the resulting mature T cells are able to recognize self-MHC without responding too strongly, which could result in autoimmune reactions. The CD4 and CD8 coreceptors play an important role in the selection processes, and the class of self-MHC that was recognized by the cell will dictate whether CD4 or CD8 expression remains on the cell while the other is downregulated. CD4 corresponds to the recognition of MHC class II while CD8 corresponds to MHC class I. The cell will then proceed into the single-positive (SP) phase, producing mature, naive CD4-positive or CD8-positive, alpha-beta thymocytes. Cells are generally committed to the CD4 or CD8 lineage at this stage. These cells will complete their development by tuning their TCR threshold and proliferation, then migrate to the periphery as mature, naive T cells. CD4-positive, alpha-beta thymocytes, upon exiting the thymus, develop into CD4-positive T helper cells. These cells play a crucial role in the immune response. They do not directly kill infected cells or pathogens; instead, they 'help' other cells in the immune system to accomplish this. Their functions include activating and directing other immune cells, stimulating B cells to produce more antibodies, and secreting cytokines to regulate the immune response, among others. (This extended description was generated by ChatGPT and reviewed by the CellGuide team, who added references, and by the CL editors, who approved it for inclusion in CL. It may contain information that applies only to some subtypes and species, and so should not be considered definitional.) CD4-positive, alpha-beta immature T lymphocyte thymocyte CD4 molecule T-cell surface glycoprotein CD8 alpha chain thymus