MBBS Batch 30: Basics of Immunity I

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Questions and Answers

What is the main function of the immune system?

The immune system protects the body from harmful substances, germs, and cell changes that could make you ill.

What are the three main types of immunity?

Innate, Acquired, Specific

Innate, Acquired, Adaptive (correct)

Passive, Active, Humoral

Natural, Artificial, Acquired

What are the two main categories of acquired immunity?

Active and passive immunity

What are the cell types involved in cell-mediated immunity?

T cells and macrophages Signup and view all the answers

What is the role of MHC II in the immune system?

MHC II is a marker on B cells that helps present antigens to T cells. Signup and view all the answers

Memory B cells and memory T cells both play a role in long-term immunity.

True Signup and view all the answers

Which type of immunity is responsible for the production of antibodies?

Humoral immunity Signup and view all the answers

What are the three lines of defense in the human immune system?

The first line of defense is physical and chemical barriers. The second line of defense is non-specific innate responses. The third line of defense is specific adaptive responses. Signup and view all the answers

Which of the following is NOT a component of the first line of defense in innate immunity?

Phagocytes Signup and view all the answers

How do cytokines contribute to inflammation?

Cytokines are signaling proteins that help control inflammation in the body. They allow the immune system to mount a defense. Signup and view all the answers

The inflammatory response is a specific response to a particular pathogen.

False Signup and view all the answers

What are the two major pathways involved in the adaptive immune response after T cell activation?

One pathway involves cytotoxic T cells and the other involves B cells. Signup and view all the answers

What is the difference between innate and acquired immunity?

Innate immunity is present at birth and provides a general, non-specific defense, while acquired immunity develops throughout life and provides specific protection against pathogens. Signup and view all the answers

Which of the following is a key characteristic of passive immunity?

It is acquired through the transfer of antibodies Signup and view all the answers

What are the two main types of cells involved in adaptive immunity?

B lymphocytes (B cells) and T lymphocytes (T cells) Signup and view all the answers

Adaptive immunity does not require prior exposure to an antigen.

False Signup and view all the answers

Which type of immunity is responsible for the rejection of transplanted organs?

Cell-mediated immunity Signup and view all the answers

What role do natural killer cells play in the immune system?

Natural killer cells are part of the innate immune system, and they are critical for destroying cells that have become infected or cancerous. Signup and view all the answers

Study Notes

MIHS (65102) MBBS Batch 30, Lecture 2: Basics of Immunity I

The lecture discusses the types of immunity, the cells and organs of the immune system, and the factors that determine antigenicity.
Students will be able to classify immunity and describe the lines of defense of immunity after the lecture.
They should also be able to differentiate between innate and acquired immunity, active and passive immunity, natural and artificial immunity.
The primary and secondary lymphoid organs, and the different cells involved in immunity will also be covered.
Important terms such as antigen, immunogens, hapten, epitope, adjuvant, superantigen, and heterophile antigen will be explained.
The factors that determine antigenicity will also be discussed and studied.

Function of the Immune System

The immune system protects the body from harmful substances, germs, and cell changes that can make you ill.

Why Study Immunology?

It is important for prophylactic measures (like vaccines).
It is important for diagnosis (lab tests involving antibodies and antigens).
It is important for therapy, including treatment for cancer.

Immunity

Immunity refers to the body's ability to fight pathogens.
The immune system identifies foreign antigens and makes antibodies against them.
Important components of the immune response are white blood cells and antibodies (IgA, IgE, IgG, IgM, and IgD).
These antibodies are globular proteins which act on antigens or activate killer T cells to eliminate pathogens.

Classify Immunity

This topic is presented, but no specific details are given.

Immunity and its Types

Immunity is categorized as innate and adaptive immunity.
Innate immunity is further divided into natural and artificial, and passive and active immunity.
Active immunity is acquired through exposure to a pathogen, and passive immunity comes from receiving antibodies from another source

Component of Innate Immunity

The bodies first line of defence.
Physical barriers such as skin and mucous membranes.
Cells, such as granulocytes, monocytes, and macrophages.
Chemical barriers like pH and enzymes.

Innate Immunity depending on their action on the pathogen

A distinction between specific and non-specific immunity is presented.
Non-specific immunity is based on immunoglobulins (IgA, IgD, IgE, IgG, IgM). These attack pathogens.
Cells involved include dendritic cells, mast cells, neutrophils, eosinophils, macrophages, and natural killer cells.

Nonspecific Immunity

First line of defense: mechanical barriers (skin, mucous membranes), chemical barriers (acid, tears), and reflexes (sneezing, coughing).
Second line of defense: phagocytosis, inflammation, fever, protective proteins (interferons, complement).

Nonspecific Resistance

The first line of defense includes intact skin, mucous membranes and secretions, and normal microbiota.
The second line of defense includes phagocytic white blood cells, inflammation, fever, and antimicrobial substances.

Specific Resistance (Acquired Immunity)

The third line of defense involves specialized lymphocytes (B cells and T cells) and antibodies.

Adaptive or Acquired Immunity

Adaptive immunity develops throughout life, unlike innate immunity.
It responds to a specific antigen, producing specific antibodies that remember the antigen for future encounters, thereby providing lasting protection.
Adaptive immunity is divided into active and passive immunity.
Active immunity is developed following exposure to a pathogen, where the body produces antibodies, and passive immunity involves receiving antibodies from another source (like a mother's milk or an injection).

Acquired Immunity (Active and Passive)

Active immunity is produced actively by the host's immune system following exposure to an antigen (infection or immunization).
Passive immunity is produced by administering preformed antibodies (e.g., through antibody transfer in maternal or artificial means).

Components of Adaptive Immunity

Immunoglobulins protect against toxins and pathogens.
Macrophages and CTLs destroy pathogens, cancer cells, and transplanted tissues.

Active Immunity and Passive Immunity

Active Immunity: Resistance developed in response to an antigen.
Passive Immunity: Resistance acquired through preformed antibodies.

Describe the lines of defense of immunity.

Three lines of defense have been described

Function of Immune cells

Recognize pathogen
React: Kill pathogens, stimulate wound healing, clear debris, coordinate immune response.
Regulate: Control immune cells from destroying themselves.
Remember: T and B lymphocytes respond to previous infections.

Myeloid Lineage

Immune cells originate from Hematopoietic stem cells (HSCs).
Myeloid cells produce granulocytes, erythrocytes, platelets, monocytes.
Specialized cells such as macrophages, mast cells and dendritic cells are also produced.

Lymphoid Lineage

Lymphoid stem cells develop into different types of lymphocytes, including natural killer cells, T cells and B cells.

Cells of the adaptive immune system (Lymphocytes)

B cells are involved in the humoral immune response.
T cells mediate cellular immune response.

Types of T cells

Killer T cells: destroy cancerous or infected cells
Helper T cells: activate B cells, produce cytokines.
Regulatory T cells: tone down the immune response and kill killer T cells

B Lymphocyte and T Lymphocyte

B cells mature in the bone marrow.
T cells mature in the thymus.

How does the immune system protect from foreign invaders?

The human body has three lines of defense against foreign invaders.
The first line involves physical and chemical barriers.
The second line involves non-specific innate responses.
The third line involves specific adaptive responses.

1st line of defense (Innate Immunity)

External barriers: Skin, hair, sweat, mucous membranes, saliva, and tears.
These create physical and chemical barriers to destroy pathogens.

2nd line of defense (Innate Immunity)

Internal barriers. Phagocytes engulf and destroy pathogens.
Inflammation is a localized tissue response to stimuli, bringing white blood cells to the site.
Fever inhibits bacterial growth.

3rd line of defense (Adaptive Immunity)

Lymphocytes (B and T cells) recognize and respond to specific antigens
Cell-mediated immunity
Humoral immunity

Humoral Immunity/B-cells

B cells are responsible for antibody-mediated immunity.
they produce antibodies that recognize and target specific antigens.
plasma cells and memory B cells are crucial to this process.

Cell-Mediated/T Cell Immunity

T cells are crucial in cell-mediated immunity.
Different T cell types, such as helper T cells and cytotoxic T cells, have distinct roles in the immune response.
Memory T cells provide long-term protection against re-infection.

Adaptive Immunity

Initiated when innate immune response fails
Antigen and activated antigen-presenting cells are delivered to draining lymphoid tissues.

Humoral response and Cellular response

The humoral response involves B cells producing antibodies.
The cellular response involves T cells targeting and destroying infected cells.

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Description

This lecture covers the fundamentals of immunity, focusing on the types of immunity and the structure of the immune system. Students will learn to differentiate between various forms of immunity, such as innate vs. acquired and active vs. passive. Key terms and concepts related to immunity, including lymphoid organs and antigenicity, are also explored.