Lego recreation of Antibody Antigen Binding

When the Immune System has a Meltdown

Tutoring A level biology allows me to indulge in one of my passions of biochemistry. The immune system. To me, immunology is one of the most fascinating topics of the biology curriculum. Unfortunately, many of my students are unable to feel the same way. Immunity is quite difficult to understand and is taught at a low threshold in the current A level syllabus. This means that the detail that make immunity so very clever, is missing.

The immune system works as a very finely tuned machine – like a high-performance car. While everything is working to order, the car behaves beautifully but as one piece breaks down, so there is a knock-on effect on the other parts and the car functions less and less well as more pieces are affected.

The immune system, when it functions properly, is able to detect body cells as ‘self’. In other words, your immune system can tell what cells and tissue are yours – and it will leave them well alone. The immune system only responds to molecules that it recognises as ‘foreign’ or ‘non-self’ and these molecules are termed antigens. The cells of the immune system, in recognition of the foreign antigen, get on with the important job of making specific antibody that are able to bind to, and eliminate these foreign antigens.

Autoimmune disease is a very generic term that covers a basic malfunction of the immune system and can potentially affect every tissue in the body. The immune system fails to recognise a ‘self’ molecule on the surface of a ‘self’ cell and this triggers antibody production. These antibodies then bind to the patient’s own tissue and target that tissue for destruction – in much the same way that the immune response would target invading bacteria.

A common autoimmune disease, and one that many of my students can identify with, is rheumatoid arthritis. Many students have an older relative with RA and understand the symptoms of stiffness, joint pain and decreased mobility. Some joints of the body are encapsulated in a membrane called a synovial membrane, and contain fluid called synovial fluid. Initially inflammation occurs in these joints, and there is an influx of various cells of the immune system into the synovial fluid. The abnormal cellular activity further damages the bone of the joint, and in turn this leads to more inflammation. So, the cycle continues. Over time, joint damage increases and normal function of the joint decreases. This is accompanied by increased antibody production and increased immunological activity. Once the antibodies are present and circulating, other joints become affected. Unfortunately, the only option for treatment is to counteract the pain and limit the activity of the immune system. It is unlikely that the process, once started, is reversible.