Question

Give a brief account of the immune system.

Answer 1

• The immune system is a host defence system comprising many biological structures and processes within an organism that protects against disease.
• To function properly, an immune system must detect a wide variety of agents, known as pathogens, from viruses to parasitic worms, and distinguish them from the organism's own healthy tissue.
• In many species, the immune system can be classified into subsystems, such as the innate immune system versus the adaptive immune system, or humoral immunity versus cell-mediated immunity.
• Pathogens can rapidly evolve and adapt, and thereby avoid detection and neutralization by the immune system; however, multiple defence mechanisms have also evolved to recognize and neutralize pathogens.
• Even simple unicellular organisms such as bacteria possess a rudimentary immune system in the form of enzymes that protect against bacteriophage infections.