Topics: Immune system / Pages: 9 (2125 words) / Published: Apr 2nd, 2013
Internal Defences

Syllabus Content
Specific resistance: * role of B cells, T cells, memory cells and plasma cells * antibody and cell-mediated defence * primary and secondary immune response * passive and active immunity * natural and artificial immunity * role of antibiotics and antivirals.

Risks, ethical concerns and benefits: * production and use of vaccines

Review of Body’s Defences Pathogens – living organisms or agents that cause disease (e.g. bacteria, fungi, parasites, viruses and prions) Non-self – any pathogen or foreign substance not recognised as part of an individual Non-specific – a line of defence that prevents the entry or effect of any non-self material Macrophage – mobile white blood cells that engulf and destroy pathogens through the process of phagocytosis The Lymphatic System The lymphatic system is found throughout the body and has its own network of capillaries and vessels. It contains a clear fluid known as lymph that can circulate between the blood vessels, tissue fluid and lymphatic vessels. As the fluid enters the lymphatic vessels it encounters white blood cells that monitor the body for ‘non-self’ substances. This primarily happens at the lymph nodes. Specific Defences Our body has the ability to target and resist a particular non-self substance (now known as an antigen) if it penetrates the non-specific defences. This is known as specific immunity. Specific immunity is achieved through the immune response – a very complex process that involves non-specific cells like macrophages as well as cells known as lymphocytes. Lymphocytes Lymphocytes are made in the bone marrow in the hollow of long bones. From here, two types of lymphocytes start – B cells and T cells. The B cells continue the maturation process in the bone marrow. T Cells, however, mature in the thymus. Once mature, B and T cells migrate to lymphoid tissue throughout the body but become mainly concentrated in the lymph

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