hjælperTceller

HjælperTceller, known in English as helper T cells, are a subset of CD4+ T lymphocytes that play a central role in coordinating adaptive immune responses. They do not typically kill pathogens directly but orchestrate the activity of other immune cells, including B cells, cytotoxic T cells, and macrophages.

Development and markers: They arise from hematopoietic stem cells in the bone marrow and mature in the thymus. After activation, hjælperTceller differentiate into several functional subsets, including Th1, Th2, Th17, Tfh, and regulatory T cells (Tregs). Each subset is associated with distinct cytokine profiles and roles.

Activation and function: Activation requires recognition of a peptide antigen presented on MHC class II molecules by professional antigen-presenting cells, along with co-stimulatory signals such as CD28. Activated hjælperTceller secrete cytokines that promote B cell antibody production and class switching, support germinal center reactions, activate cytotoxic T cells, and enhance macrophage microbicidal activity. The specific cytokine milieu determines the downstream response; for example, Th1 cells promote macrophage activation and responses against intracellular pathogens, while Th2 cells support humoral immunity and defenses against extracellular parasites and can be involved in allergic responses.

Clinical relevance: HIV infection targets CD4+ T cells, leading to immunodeficiency. Dysregulation or imbalance of hjælperTceller subsets has been implicated in autoimmune diseases, allergies, and inflammatory conditions. Vaccination strategies often aim to elicit strong hjælperTceller responses to generate robust antibody and cytotoxic T-cell immunity.

See also: CD4+ T cells, MHC class II, antigen presentation, cytokines.