Adaptive Immunity Overview

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the function of the Major Histocompatibility Complex (MHC) in antigen presentation?

It destroys pathogens by phagocytosis using specialized enzymes.

It produces cytokines that activate T cells during inflammation.

It displays fragments of digested antigens on the surface of antigen presenting cells. (correct)

It binds to B cell receptors to initiate humoral immunity.

Which of the following types of T cells suppress the immune response?

Memory T cells

Helper T cells

Cytotoxic T cells

Regulatory T cells (correct)

In cell-mediated immunity, which type of T cell is responsible for directly killing foreign or infected host cells?

Regulatory T cells

Cytotoxic T cells (correct)

B cells

Helper T cells

What happens first when an antigen invades the body?

Antigen presenting cells digest the antigen into particles. Signup and view all the answers

What is the normal range of T cell count in healthy individuals?

600 – 1200 cells/μl Signup and view all the answers

What is the main function of the constant fragment (Fc) of an antibody?

To mediate physiological effects through Fc receptors Signup and view all the answers

Which of the following statements is true regarding the structure of antibodies?

Antibodies have a Y shape formed by four polypeptide chains Signup and view all the answers

Which immunoglobulin type is mainly responsible for being transported across the placenta?

IgG Signup and view all the answers

What characteristic distinguishes IgM from the other immunoglobulins?

It is a pentamer consisting of five Ig units Signup and view all the answers

Which of the following statements about IgA is correct?

It is primarily found in secretions and often exists as a dimer Signup and view all the answers

Which of the following is NOT a feature of adaptive immunity?

Recognizes antigens with low specificity Signup and view all the answers

What is the primary role of B lymphocytes in adaptive immunity?

Produce antibodies Signup and view all the answers

Which statement best describes clonal selection?

Activated lymphocytes divide to form clones Signup and view all the answers

Where do T lymphocytes mature?

Thymus Signup and view all the answers

Which component is crucial for the recognition phase of adaptive immunity?

Specific receptors on lymphocytes Signup and view all the answers

What initiates the response phase of the adaptive immunity?

Cytokine secretion Signup and view all the answers

How do memory cells contribute to adaptive immunity?

They provide a faster response upon re-exposure to the same antigen Signup and view all the answers

Which of the following statements regarding antibody responses is accurate?

Primary responses take time due to clonal selection and activation Signup and view all the answers

Study Notes

Adaptive Immunity Lecture Notes

Adaptive immunity is not innate; it develops throughout life.
It's slower than the innate system but highly specific.
It has a memory function, adapting to repeated exposures.

Learning Objectives

Understanding the features of adaptive immunity.
The 3 Rs of adaptive immunity (Recognize, Respond, Remember).
Clonal selection.
Cell-mediated immunity.
3 types of T cells.
Antigen presentation.
Antibody-mediated (humoral) immunity.
B cells.
Antibody structure and function.
Primary and secondary antibody responses.

Cells Involved

Lymphocytes are central to adaptive immunity.
- B lymphocytes produce antibodies.
- T lymphocytes are involved in cell-mediated immunity.
T cells mature in the thymus.
B cells mature in the bone marrow.

Principles of Adaptive Immunity

Each lymphocyte has a specific receptor for a particular antigen.
Innate immune cells help with recognition.
This recognition is followed by clonal selection.
Adaptive responses include cytokine secretion, antibody production, and direct cell killing.
Memory cells are crucial for quicker responses in subsequent encounters with the same antigen.

Clonal Selection

(Burnett, 1957) Lymphocytes have receptors to bind a single antigen.
Lymphocyte repertoire is highly diverse with varied specificity.
When an activated lymphocyte encounters its antigen, it becomes activated and multiplies rapidly to create a clone of effector and memory cells.
Effector cells directly combat the antigen.
Memory cells provide a rapid response to subsequent exposures.

Clonal Selection (Diagram Explanation)

Primary response: Recognition and activation of naïve B cells, followed by the formation of clones and antibody production by plasma cells.
Secondary response: Memory B cells rapidly produce large amounts of antibody upon re-exposure; the antibody response is much faster, stronger, and more focused.

Cell-mediated Immunity

T cells require antigen-presenting cells (APCs) to process and present antigens.
APCs include phagocytes, dendritic cells, and macrophages.
APCs display digested antigen fragments on their MHC (Major Histocompatibility Complex).
This presentation activates T cells.
After activation, helper T cells enhance the immune response, cytotoxic T cells directly kill infected cells, and regulatory T cells suppress unnecessary responses.

Antigen Presentation (Detailed)

Antigens invade the body.
Phagocytosis by antigen-presenting cells (APCs).
Digestion of antigen into smaller particles.
Transport of these particles to the cell surface.
Display on surface via MHC molecules.

T Cell Types

Regulatory T cells (Tregs): Suppress immune responses.
Helper T cells: Activate B cells and other immune cells.
Cytotoxic T cells: Kill infected host or foreign cells.

B Cells & Antibodies (Humoral Immunity)

B cell receptors (BCRs) are antibodies that directly bind antigens.
BCRs recognize specific epitopes (antigenic determinants) on antigens.
After clonal selection and expansion, B cells produce antibodies with the same specificity as their BCRs.

Antibodies

Antibodies (Immunoglobulins): Y-shaped proteins with two identical heavy chains and light chains.
Two antigen-binding sites (Fab).
Stem (Fc) region binds to Fc receptors.
Antibodies mediate various immune responses, including neutralizing, opsonization, and complement activation.

Antibody Structure Details

4 polypeptide chains with consistent and variable regions.
Antigen-binding sites are variable.
Stem region is constant across antibody types.

Antibody Isotypes

Five main types (IgG, IgM, IgA, IgD, IgE) with distinct roles in immunity. IgG is a major one, present in high concentrations. IgM is used to recognize pathogens. IgA is present in secretions. IgD is found on B-cell surfaces. IgE is involved in allergies.

Functions of Antibodies

Neutralization: Blocking pathogen binding to cells.
Opsonization: Enhancing phagocytosis by tagging pathogens.
Antibody-dependent cellular cytotoxicity (ADCC): NK cells killing antibody-coated cells.
Complement activation: Cascade of proteins that enhances pathogen destruction.
Inflammation: Initiating inflammation response.

Primary vs. Secondary Antibody Response

Primary response: 5-10 days, low titre, mainly IgM.
Secondary response: 1-3 days, high titre, mainly IgG, more antibody specificity, affinity maturation.

Immunological Memory

A faster, larger, and more effective response upon subsequent antigen encounters due to memory cells.

Summary of Main Points

Adaptive immunity is specific, adaptable, and has immunological memory.
Clonal selection creates a specific immune response.
Antigen presentation is essential for T-cell activation.
B cells produce antibodies.
Different antibody isotypes have unique functions.
Secondary responses are superior to primary responses due to the presence of memory cells.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the key concepts and principles of adaptive immunity in this quiz. Understand the roles of B and T lymphocytes, the mechanisms of antibody production, and the importance of memory in immune responses. This content is essential for grasping the complexity of how our immune system protects us over time.