Antibodies in action. Artwork of antibodies (light to dark pink) in blood attacking an invading bacterium (left) and virus particle (centre right, green). Antibodies are Y-shaped proteins made by the immune system in response to infection by bacteria, viruses or allergens. Each antibody is made to recognise a specific target antigen and bind themselves to the surface. Binding can neutralize toxins or invading organisms and prevent them from interfering with normal cell processes. Binding can also make it easier for white blood cells to recognise and digest foreign particles.