Methods of Specific Defence Used by the Human Body

Specific defence, also referred to as adaptive immunity, plays a crucial role in human health by defending against specific pathogens or foreign substances.
The key components of specific defence are lymphocytes: B-cells and T-cells, which develop in the bone marrow and thymus respectively.
B-cells are responsible for humoral immunity. They produce antibodies against specific antigens, leading to their neutralisation.
Each B-cell generates a unique antibody that can bind with a specific antigen. When an antigen matches with its corresponding B-cell, the cell is stimulated to reproduce, creating a clone of B-cells that produce the same antibody.
Antigens and antibodies bind together in a lock-and-key model. Each antibody has a specific shape that corresponds to a specific antigen.
T-cells are involved in cell-mediated immunity. They identify infected host cells and facilitate their destruction.
There are several types of T-cells, including helper T-cells (Th), cytotoxic T-cells (Tc), and Memory T-cells. Th cells recognise foreign antigens and stimulate B-cells or Tc cells, Tc cells destroy infected host cells, and Memory T-cells remember specific antigens to enable a faster response to future exposures.
Specific defence also includes immune response mechanisms like clonal selection, where the body selects a type of lymphocyte to replicate and fight off an infection, and immunological memory, where the immune system remembers past pathogens for a quicker response in future encounters.
Vaccination is a biomedical strategy that exploits the specific defence mechanisms. It artificially introduces an antigen to stimulate the production of antibodies and memory cells, which will then respond more rapidly when the genuine pathogen is encountered.
Specific defence is critical for long-term immunity but it takes time to fully establish compared to non-specific defence. This is because it needs to recognise the antigen, generate a response and then remember the antigen for future invasions.
Understanding the complexities of specific immunity has led to important biomedical developments in areas such as vaccine production, cancer treatment, and understanding auto-immune diseases.