Antigens are molecules or substances that are recognized by the immune system as foreign or non-self. These can include proteins, polysaccharides, glycoproteins, and other molecular structures present on the surface of pathogens such as bacteria, viruses, fungi, or parasites. Antigens can also be found on the surface of transplanted tissues or cells from another organism.
In laboratories, antigens are generated through methods tailored to their specific characteristics and intended use. Recombinant DNA technology involves inserting the antigen-coding gene into host organisms like bacteria or yeast, enabling production and subsequent purification. Chemical synthesis, particularly suitable for small antigens like peptides, constructs antigen molecules step by step via organic chemistry techniques. Antigens can be isolated and purified from natural sources such as viruses or tissues or expressed in cell-free systems, where purified cellular components translate mRNA molecules into protein. Hybridoma technology fuses antibody-producing B cells with immortalized myeloma cells to create hybridoma cells generating monoclonal antibodies against target antigens, facilitating antigen detection or purification. Peptide libraries offer a method to synthesize a range of potential antigenic peptides, allowing for screening to identify specific epitopes.
Once generated, antigens undergo purification to eliminate contaminants and ensure their suitability for various applications, including research, diagnostics, or biologic development. The choice of production method depends on factors such as antigen size, complexity, and intended use.