As stated earlier, this course requires a basic knowledge of immunology. For review, here is a simplified overview of the immune response:
The immune response can be divided into innate immunity and adaptive immunity.
1. Innate immunity occurs immediately and recognizes and responds to pathogen-associated molecular patterns (PAMPs). PAMPs are molecular patterns that types of pathogens possess, such as certain features that a range of viruses, bacteria, or fungi have in common but that are not found in humans. The innate immune cells have receptors on their surfaces, such as the Toll-like receptors (TLRs) which recognize the PAMPs. Two of their important functions are:
- Innate cells respond quickly and broadly, and their activity leads to inflammation. Many, although not all of the innate cells, use the process of phagocytosis to engulf and destroy the pathogen.
- Innate cells activate adaptive immunity by secreting special chemicals called cytokines that orchestrate the immune response, and also by preserving bits of the pathogen that was phagocytized and "presenting" it to lymphocytes.
Examples of innate cells are macrophages, monocytes, neutrophils, and dendritic cells. Basically, the immune cells other than lymphocytes. These cells develop in the bone marrow and when mature, they exit into the bloodstream. From there they will migrate into tissues where there is a potential infection. They typically function the same each time, no matter how many times the pathogen invades the body. That is to say, they don't possess memory, which is a hallmark of the adaptive response.
2. Adaptive immunity requires up to two weeks to fully develop and is highly specific for the part of the pathogen that is recognized. The adaptive cells are lymphocytes, of which the major groups are known as T cells and B cells. They possess highly specific T-cell receptors (TCRs) and B-cell receptors (BCRs). These TCRs and BCRs will recognize specific parts of the pathogen known as antigens, rather than patterns of molecules. These antigens are molecules that bind to each unique receptor. A human has billions of different TCRs and BCRs.
When the lymphocytes develop in the bone marrow (B cells) or thymus (T cells), their genes undergo a process of gene recombination and rearrangement, in which germline genes from a potential original group randomly are chosen to recombine to form a new blueprint. Gene recombination enables the formation of many different receptors, despite the fact that we only have a limited number of genes to begin with.
