The adaptive immune response
When pathogens are not destroyed by the innate immune system, the adaptive immune response takes over. This is a highly specific response that involves specialised cells called lymphocytes and takes place in the lymphatic system . There are two paths of the adaptive immune response: the humoral response that uses antibodies, and the cell-mediated response which uses cytotoxic T cells.
Use this page to revise the following concepts within the adaptive immune response:
The Humoral Response
The humoral response is commonly activated to fight bacterial infections or toxins. and relies on using antibodies to destroy the foreign antigens. In contrast, the other immune response, the cell-mediated response , uses cells to fight an infection.
The response is tightly regulated, and involves several steps of clonal selection: specific cells are selected and cloned to fight a specific target. Cells that are clonally selected will then clonally select other immune cells, creating a rapid expansion in the number of lymphocytes targeted to a specific pathogen. This rapid expansion of lymphocytes is one reason an infected person may feel fatigue.
Investigate the activation of the humoral response by interacting with the following figure.
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Antibodies
Antibodies are small Y shaped proteins that are secreted by Plasma B cells. They destroy or deactivate the pathogen when they bind to it. They are highly specific to a particular antigen. The level of antibodies in your blood can indicate the strength of your immunity to that specific pathogen.
Explore the structure of the antibody and the four main ways antibodies function when binding to pathogens with the image below.
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Cell-mediated response
The cell-mediated response is the other path of the adaptive immune response. It is commonly activated to fight cancerous cells or cells that have been infected by viruses. The cell-mediated response relies on using cells (e.g. cytotoxic T cells) to destroy other diseased cells, hence the name ‘cell-mediated’. This differs from the humoral response that uses antibodies to fight an infection.
Like the humoral response, the cell-mediated response involves a cascade of cells being activated and dividing. This large consumption of resources contributes to the symptoms a sick person may feel, such as fatigue.
Explore the cell mediated immune response by clicking on the hotspots in the image below.