Unit 8.2: Adaptive Immunity
Outline
Part 1: Overview of Specific Adaptive Immunity
Part 2: Major Histocompatibility Complexes and Antigen Presenting Cells
Part 3: T Lymphocytes and Cellular Immunity
- T Cell Production and Maturation
- Classes of T cells
- Activation and Differentiation of Helper T Cells
- Activation and Differentiation of Cytotoxic T Cells
Learning Objectives
After reading the following, you should be able to:
- Describe two differences between innate and specific immunity.
- Define: humoral vs. cell-mediated immunity, antibodies, antigen, epitopes, hapten
- Describe the activation of a helper T cell and the function of a helper T cell.
- Describe and give an example of cytokines important to the adaptive immune system.
- Describe the activation of a B cell against T-independent, and against T-dependent antigens and the function of a B cell.
- Describe the structure and function the five types of antibodies.
- Explain how a cytotoxic T cell is activated and the function of a cytotoxic T cell.
- Describe the two ways that a cytotoxic T cell can kill a body cell.
- Explain why a secondary response is much stronger than a primary response to a specific antigen
- Describe the function of vaccinations.
- Name and describe the different types of vaccines.
Part 1: Overview of Specific Adaptive Immunity
Adaptive immunity, often considered the third line of immune defense, is defined by two important characteristics: specificity and memory. Specificity refers to the adaptive immune system’s ability to target specific pathogens, and memory refers to its ability to quickly respond to pathogens to which it has previously been exposed. For example, when an individual recovers from chickenpox, the body develops a memory of the infection that will specifically protect it from the causative agent, the varicella-zoster virus, if it is exposed to the virus again later.
Specificity and memory are achieved by essentially programming certain cells involved in the immune response to respond rapidly to subsequent exposures of the pathogen. This programming occurs as a result of the first exposure to a pathogen or vaccine, which triggers a primary response. Subsequent exposures result in a secondary response that is faster and stronger as a result of the body’s memory of the first exposure (Figure 8.20). This secondary response, however, is specific to the pathogen in question. For example, exposure to one virus (e.g., varicella-zoster virus) will not provide protection against other viral diseases (e.g., measles, mumps, or polio).
Adaptive specific immunity involves the actions of two distinct cell types: B lymphocytes (B cells) and T lymphocytes (T cells). Although B cells and T cells arise from a common hematopoietic stem cell differentiation pathway (see Figure 8.10), their sites of maturation and their roles in adaptive immunity are very different.
B cells mature in the bone marrow and are responsible for the production of glycoproteins called ant