Explain adaptive immunity

The adaptive, or acquired, immune response takes days or even weeks to become established—much longer than the innate response; however, adaptive immunity is more specific to pathogens and has memory. Adaptive immunity is an immunity that occurs after exposure to an antigen either from a pathogen or a vaccination. This part of the immune system is activated when the innate immune response is insufficient to control an infection. In fact, without information from the innate immune system, the adaptive response could not be mobilized.

There are two types of adaptive responses: the cell-mediated immune response, which is carried out by T cells, and the humoral immune response, which is controlled by activated B cells and antibodies. Activated T cells and B cells that are specific to molecular structures on the pathogen proliferate and attack the invading pathogen. Their attack can kill pathogens directly or secrete antibodies that enhance the phagocytosis of pathogens and disrupt the infection. Adaptive immunity also involves a memory to provide the host with long-term protection from reinfection with the same type of pathogen; on re-exposure, this memory will facilitate an efficient and quick response.

What You’ll Learn to Do

• Describe the structure and function of antigen-presenting cells
• Describe the structure and function of T lymphocytes
• Describe the structure and function of B lymphocytes
• Describe immune tolerance
• Describe the role and importance of immunological memory
• Identify the primary centers of the immune system

Learning Activities

The learning activities for this section include the following:

• Antigen-Presenting Cells
• T and B Lymphocytes
• Mucosal Surfaces and Immune Tolerance
• Immunological Memory
• Primary Centers of the Immune System
• Self Check: The Adaptive Immune Response