Immunologic memory is composed of memory T and B cells and provides the immune system with specific information about particular pathogens. This allows the immune system to fight disease more effectively and quickly after initial infection. In autoimmune diseases, faulty information is probably stored in the immunological memory.
What is immunologic memory?
The memory T cells and memory B cells of the immune system are grouped together as immunologic memory. Specifically, white blood cells (leukocytes) and their subset, lymphocytes, perform immunological functions in the organism of higher organisms. The T memory cells and the B memory cells of the immune system are summarized as immunological memory. Especially the white blood cells (leukocytes) and their subgroup, the lymphocytes, take over immunological functions in the organism of higher living beings. T and B memory cells are specialized subgroups of T and B lymphocytes. Both B and T lymphocytes are capable of producing antibodies and are part of the adaptive immune system, which reacts with humoral and cellular immune responses to foreign antigens. B- or T-cells are activated at the first contact with a specific antigen. As a result, a large proportion of them die. The remaining cells can develop into memory cells. Upon renewed contact with the antigen, they are activated with immediate effect and “remember” the antigen in question. In this way, they trigger the learned immune responses in a very short time, which prevent the outbreak of an infection. The first speculations about the existence of an immunological memory occurred in the 19th century, when a measles epidemic broke out in the Faroe Islands and protection against a new disease was observed.
Function and task
Immune responses are either humoral or cellular. Pathogens in the blood or lymph trigger humoral immune responses. Plasma proteins in the form of immunoglobulins are present in body fluids to combat antigens. The cellular immune response is not controlled by immunoglobulins, but specifically by T lymphocytes. They move around in the blood and lymph fluid and dock with their receptors to antigen-representing cells to trigger cell death. Activation of T and B cells by contact with a pathogen transforms them into memory cells. Memory B cells thus form the information store for antibody formation against diseases that an organism has previously contracted. Every humoral immune response activates B cells, which carry suitable antibodies on their surface for fighting. The B cells divide after activation. Some of the cells become plasma cells. The remaining B cells turn into memory B cells. When the body comes into contact with the pathogen again and a humoral immune response is required, memory B cells transform into plasma cells at breakneck speed. Even before an infection breaks out, an antibody response is thus triggered. With regard to T cells, a similar process takes place. Stimulation of the immune system with an antigen causes specific T cells to multiply tenfold to a hundredfold. Most of the T cells have a short lifespan and die pre-programmed cell death after an immune response. About five percent of the cells survive the immune response. These cells transform into long-lived memory cells and ensure a rapid immune response after repeated contact with the antigen. The immunological memory of humans thus stores information about specific pathogens and makes it available to the organism. The memory cells are supported in their survival by eosinophil granulocytes. Thus, the immune system is capable of learning, adaptive and therefore more effective. The stored information in the immunological memory is available to the defense system of the organism for several decades because of the longevity of the memory cells.
Diseases and ailments
Autoimmune diseases anchor in malfunctions and misinformation stored in immunological memory. In rheumatism, multiple sclerosis or the intestinal disease Crohn’s disease, the body therefore fights itself.In a healthy person, the immune system recognizes certain pathogens as foreign thanks to immunological memory and knows exactly which antibodies to send out to fight them. In autoimmune diseases, the immune system no longer succeeds in distinguishing between foreign substances and the body’s own substances. Therefore, antibodies are sent out against the body’s own tissue. Until now, autoimmune diseases have been considered incurable. With drugs such as immunosuppressants, the destructive attacks against the body’s own tissue can be suppressed, delayed or at least weakened. Immunological memory has its headquarters in the bone marrow, where memory plasma cells are produced and survive for years. A relatively new approach to curing autoimmune diseases is being discussed with the removal of eosinophilic granulocytes from the bone marrow. Since granulocytes help memory cells survive, their removal would drive the cells to death. Regulating an overactive immune system by temporarily removing granulocytes from the bone marrow could erase the immunologic memory that accounts for autoimmune disease. Experience in cancer patients with additional autoimmune diseases shows that immunological memory can indeed be erased. Chemotherapy destroyed their entire immune system. With the transplantation of their own stem cells, it could be rebuilt. In a majority of cases, their immunological memory was subsequently erased and they had overcome their autoimmune disease. Despite the success of this therapeutic option, deletion of immunological memory is temporarily associated with a high risk of infection and is therefore not approved for mass use. In the future, however, it may be possible to use subtle methods to search for specific memory cells in the body that can be targeted for deletion.
