Cheese Production and Immunity: Key Concepts Explained
Cheese Production: Coagulation, Separation and Maturation
Rennet, also called rennin, is added to milk. Combined with lactic acid produced by lactic acid bacteria, the protein rennin precipitates and forms a solid mass called curd. The remaining liquid is called whey.
- Coagulation: rennet and lactic acid bacteria act on the milk, forming curd.
- Separation: curd and whey are separated by filtration. Salt is added to the curd.
- Maturation: during maturation, other bacteria intervene and are responsible for the taste and smell of the cheese.
Immunology: Antigens and Defenses
Antigens
Antigens are molecules from an organism that are recognized as foreign, triggering an immune response. Their characteristics are that they are usually large proteins or polysaccharides with a complex structure. They can be free molecules or part of biological structures. Recognition occurs through the selective binding of antigens to certain molecules called antigenic receptors.
External Defenses
External defenses are structural barriers, made up of the skin and mucous membranes. Mechanical defenses consist of expulsion systems that help drag out and expel particles and microorganisms, preventing their entry into the body. Biochemical and ecological defenses also play a role.
Nonspecific Defenses
Inflammation
Inflammation is a highly effective process that prepares the mechanisms of the response that will defend the body once an antigen has entered the invading organism.
Phagocytes
Phagocytes are a type of leukocyte in two groups: the myeloid leukocyte series, which forms in bone marrow and can move by amoeboid motion, and the lymphocyte series, whose cells are lymphocytes that produce specific antibodies.
Functions: they wander through tissues to eliminate microorganisms and any foreign structure that invades the body, through phagocytosis.
Complement System
The complement system is a set of blood plasma proteins whose function is to act as a rapid and powerful defense. It works through several mechanisms: it acts as an inflammatory mediator, participates in opsonization (facilitating the action of phagocytes), and provokes lysis of invasive cells by rupturing their plasma membrane.
Interferon
Interferon has two main actions: it prevents viral replication in cells that have not yet been destroyed by the virus, and it activates natural killer cells, some lymphocytes capable of recognizing infected cells and tumor cells and destroying them.
Specific Defenses
Specific defenses are directed exclusively against a particular type of antigen. Once an antigen is detected, a immune memory is created, allowing a faster response when the same antigen reappears.
Lymphocytes
Lymphocytes are leukocytes of the lymphatic series. They cannot form pseudopodia, nor phagocytose, and are not mobile. However, they have the capacity to recognize specific antigens and produce a specific response against particular antigens. There are three types:
- B lymphocytes: synthesize specific proteins (antibodies) in the presence of antigens. Most of these antibodies can diffuse through body fluids. This type of immunity is called humoral.
- T lymphocytes: responsible for what is called cellular immunity. They do not produce antibodies but directly destroy certain altered cells, which are therefore recognized as targets.
- Non-B, non-T lymphocytes: also destroy target cells, but in a nonspecific way.