Immunological Memory Flashcards
Immunological memory response
The adaptive immunity is responsible for the immunological memory.
We need about a week to get an initial immune response during a first time infection. If there is an inapparent reinfection (meaning that we will not get sick, since we already have antibodies produced from the first infection that will work against the infection), then the protective immunity is going to react immediately. If the infection comes back after years, then the response is also going to be immediate, due to the immunological memory.
The concept of immunological memory comes from the history of measles epidemic.
After smallpox vaccination, antibody levels show no significant decline, and the T-cell memory shows a half life of 8-15 years. Meaning that antibodies have a good immunological memory.
Memory cells
Most memory cells are in a resting state
A small percentage are dividing
The number of memory cells for a given antigen is highly regulated, remaining practically constant during memory phase.
They circulate in the blood and populate the spleen and lymph nodes.
Source of B cells and their response
An unimmunized donor will have a primary immune response with a lower affinity of the antibody, and lower somatic hypermutation, and the IgM molecules will be higher than IgGs. While for an immunized donor, a secondary immune response will have a higher affinity of the antibody, and higher somatic hypermutation, the antibodies present: IgG and IgA.
The affinity and concentration of the antibodies increases with the immunization dose.
During every response, there will be different antibodies present due to the somatic hypermutation.
T cell response
The T cells will have and initial production response with a high peak, but will drop over time, and as the production starts, the cell load will also be high, and then decrease immediately.
The naive T cells and memory T cells have requirements for survival.
The naive T cells requires signal from the contact with self-peptide MHC and cytokines so they can survive, because they survive a longer time than the naive B cells.
The activated naive T cells will produce the effector cells and the memory cells.
The effector cell will go to the site of infection and will die after they perform the action by apoptosis, but the memory cells will be long-lived and will require cytokines for survival and need contact with the self-peptide in the MHC complexes to continue to proliferate.
Central and effector memory cells are distinguished by expression of chemokine receptor CCR7.
None of them are committed.
The effector cells can give rise to memory cells, which become central memory cells (located in the spleen, lymph nodes and circulation) and effector memory cells (migrate to tissues and reside in there).
Even effector cells can become memory cells.
CD4T cells are required for the development of functional CD8 memory T cells.
Involves CD40 signaling. CD4 T cells promote the maintenance of CD8 memory cells.
Rh antibodies
If a mother has a Rh negative, so she doesn’t have the antigen, gets pregnant with a baby that is Rh positive, because the expression of Rh blood types is co-dominant with the father, she will start producing anti-Rh antibodies. This is going to be a foreign antigen, and eve though the placenta is keeping a barrier in between, there are points in the pregnancy in which the mother can be exposed to the foreign antigen, so the mother will produce antibodies against that antigen.
In between pregnancies, the mother will still keep those anti-Rh antibodies in the circulation. In the second pregnancy those antibodies can affect the fetus that will also have a positive Rh. Those antibodies will produce hemolysis on the blood cells of the baby, and it can be born with anemia.
To prevent this, during the pregnancy the mothers will be injected with antibody, so their bodies don’t make antibodies and plasma cells.
Antibody and memory lymphocytes remaining in an immunized individual can have the effect of reducing the activation of naive B and T cells on a subsequent encounter with the same antigen.
Original antigenic sin
Then a person is initially exposed to a flu virus, it is going to contain different epitopes. Now, the flu can come back multiple times throughout our lives and the immune response against the virus can be identified again. But because the virus can mutate and change, the epitopes will also be different, but the immune response will not be changes because it is reliant on memory, so the immunity will only work against the epitopes it is familiar with. But then again the virus can change every year, and there will be another infection, but we are still reliant with the antibodies from the initial epitopes. This can keep ongoing until the virus has epitopes that are completely new to your body, so it can start producing new antibodies.
