Antigenaufnahme

Antigenaufnahme refers to the process by which immune cells, particularly antigen-presenting cells (APCs) such as dendritic cells, macrophages, and B cells, internalize foreign substances known as antigens. This step is essential for initiating adaptive immune responses, as it allows the immune system to recognize, process, and present antigens to T cells.

The process begins when APCs encounter pathogens or foreign particles, which are often captured through mechanisms such as phagocytosis, pinocytosis, or receptor-mediated endocytosis. Phagocytosis involves the engulfment of larger particles like bacteria or cellular debris, while pinocytosis refers to the nonspecific uptake of extracellular fluid and dissolved molecules. Receptor-mediated endocytosis is a more selective process where specific receptors on the cell surface bind to distinct antigens or pathogen-associated molecular patterns (PAMPs), facilitating targeted internalization.

Once inside the cell, antigens are contained within endosomal compartments where they undergo enzymatic degradation. Peptide fragments derived from this degradation are loaded onto major histocompatibility complex (MHC) molecules. These MHC-peptide complexes are then transported to the cell surface, where they can be recognized by T cell receptors (TCRs) on T lymphocytes. This antigen presentation is critical for activating naïve T cells, which then proliferate and differentiate to orchestrate targeted immune responses.

Antigen uptake is influenced by various factors, including the type of antigen, the specific receptors involved, and the cellular environment. Efficient antigen capture and presentation are vital for effective immune surveillance and response, forming a cornerstone of immunological defense and vaccine efficacy.