immunecells

Immunecells, or immune cells, are the diverse group of cells that constitute the immune system and defend the body against pathogens, cancer, and foreign substances. They arise from hematopoietic stem cells in the bone marrow and differentiate into two main lineages: lymphoid and myeloid.

Lymphoid lineage yields T cells, B cells, and natural killer cells, mediating adaptive immunity and various innate-like responses. Myeloid lineage includes monocytes that become macrophages and dendritic cells, as well as granulocytes such as neutrophils, eosinophils, and basophils, which provide rapid effector functions. Dendritic cells specialize in antigen presentation to T cells.

Immunecells detect pathogens through receptors, coordinate responses via cytokines, and execute effector functions such as cytotoxic killing, phagocytosis, antibody production, and orchestrating inflammation. Some cells develop immunological memory after exposure, enabling faster responses upon re-encounter with the same pathogen.

Development and regulation: The immune cell compartment is shaped by genes, transcriptional programs, and signals from other cells. Primary lymphoid organs (bone marrow and thymus) support maturation; peripheral tissues host activation and differentiation. Tolerance mechanisms prevent attack on self tissues, while checkpoints regulate responses to prevent excessive inflammation.

Clinical relevance: Abnormalities in immunecell number or function underlie immunodeficiencies, autoimmune diseases, allergies, and cancer. Therapies increasingly target immune cells, including vaccines that prime memory, monoclonal antibodies, cytokines, and engineered cells such as CAR-T therapies that reprogram T cells to attack tumors.