week 10

Question 1

What constitutes the major defense systems of animals?

Answer 1

Animals have various defense systems against pathogens, which are agents that cause disease. These systems are based on the recognition of self and non-self molecules, encompassing both non-specific (innate) defenses, like skin barriers and phagocytic cells, and specific (adaptive) defenses, such as antibodies.

Question 2

What are the three phases of the animal defense response?

Answer 2

The defense response in animals consists of:

Recognition Phase: The organism discriminates between self and non-self.
Activation Phase: The recognition of a foreign invader mobilizes cells and molecules to fight.
Effector Phase: The mobilized cells and molecules destroy the invader.

Question 3

What are the two general types of defense mechanisms in animals?

Answer 3

Animals have two types of defense mechanisms:

Nonspecific Defenses (Innate): These act rapidly and include barriers such as skin, phagocytic cells, and molecules toxic to invaders.
Specific Defenses (Adaptive): These target specific pathogens, like antibodies, are slow to develop but long-lasting. In mammals, both systems work together in a coordinated manner.

Question 4

What are lymphoid tissues, and what does blood plasma contain?

Answer 4

Lymphoid tissues such as the thymus, bone marrow, spleen, and lymph nodes are essential parts of the defense system. Blood plasma contains ions, small molecular solutes, soluble proteins, with red and white blood cells, and platelets suspended within it.

Question 5

What is lymph, and what role do lymph nodes play in the defense system?

Answer 5

Lymph is a fluid derived from blood and other tissues. It moves into lymph system vessels, passes through lymph nodes containing lymphocytes (a type of white blood cell), and eventually joins the circulatory system. As lymph passes through lymph nodes, lymphocytes initiate an immune response if foreign cells or molecules are detected.

Question 6

Where do red and white blood cells originate?

Answer 6

Both red and white blood cells originate from multipotent stem cells in the bone marrow. These stem cells are constantly dividing and have the capability to differentiate into various types of cells.

Question 7

What are the two major families of white blood cells?

Answer 7

The two major families of white blood cells (leukocytes) are:

Phagocytes: Engulf and digest cellular debris and pathogens.
Lymphocytes: Smaller cells that are part of the adaptive immune response.
Additionally, granulocytes are a type of white blood cell with granules containing defensive enzymes.

Question 8

What are the four key protein types involved in cell-cell interactions in the mammalian defense system?

Answer 8

he four key protein types involved in the mammalian defense system are:

Major Histocompatibility Complex (MHC): MHC I proteins are found on most cell surfaces, and MHC II proteins are found on most immune system cells.

T Cell Receptors: Recognize and bind non-self molecules on other cells.

Antibodies: Produced by B cells, they bind specifically to substances identified by the immune system.

Cytokines: Soluble signaling proteins that bind to cell surface receptors and alter the behavior of the cell.

Question 9

How does skin function as a primary nonspecific defense?

Answer 9

The skin acts as a primary nonspecific defense by providing a physical barrier that bacteria, fungi, and viruses can rarely penetrate when healthy and unbroken. Additionally, normal flora such as bacteria and fungi that usually live on the body’s surfaces compete with pathogens for nutrients and space, contributing to the defense system.

Question 10

What is the role of mucous membranes and lysozyme in nonspecific defense?

Answer 10

Mucous membranes produce defensins, which are toxic to many pathogens. Defensins insert into the plasma membrane of pathogens, making them permeable. Tears, nasal mucus, and saliva contain lysozyme, an enzyme that attacks bacterial cell walls. Mucus in the nose and respiratory tract traps microorganisms, and cilia move the mucus and trapped debris towards the nose and mouth for expulsion.

Question 11

How are pathogens dealt with in the digestive tract?

Answer 11

Pathogens that enter the digestive tract are killed by gastric juices or bile salts in the small intestine. These harsh conditions are not normally survivable by pathogens, making the digestive tract a formidable barrier to infection.

Question 12

What happens when pathogens penetrate initial surfaces?

Answer 12

Pathogens that penetrate initial barriers encounter more complex nonspecific defenses, such as the activation of defensive cells and the secretion of defensive proteins like complement and interferon proteins. These defenses work together to neutralize and eliminate the invaders.

Question 13

What is the complement system in vertebrate blood, and how is it activated?

Answer 13

The complement system in vertebrate blood consists of antimicrobial proteins that can be activated by specific or nonspecific mechanisms. The proteins act in a cascade, where each protein in the sequence activates the next, contributing to the body’s defense against pathogens.

Question 14

What are the three types of defense provided by complement proteins?

Answer 14

Complement proteins provide three types of defense:

They attach to microbes and mark them for phagocytes to engulf.

They activate the inflammation response and attract phagocytes to the site of infection.

They lyse invading cells, effectively destroying them.

Question 15

What is specificity in the context of specific immunity?

Answer 15

Specificity in specific immunity refers to lymphocytes, mainly through T cell receptors and antibodies, binding to specific non-self molecules known as antigens. The specific sites on these antigens that are recognized are called antigenic determinants or epitopes.

Question 16

What are antigenic determinants?

Answer 16

Antigenic determinants are specific portions of a large molecule to which immune responses are directed. A single antigenic molecule can possess multiple, different antigenic determinants, and the host’s immune system responds to each with highly specific defenses involving T cell receptors and antibodies.

Question 17

How does the immune system distinguish self from non-self?

Answer 17

The immune system has the ability to recognize all of the body’s own antigens and not attack them. This crucial function ensures that the body’s cells and tissues are not targeted by its own immune responses.

Question 18

What is the importance of diversity in the immune system?

Answer 18

Diversity in the immune system is vital as it allows the body to respond to a wide variety of pathogens, including different varieties or strains of each pathogen. Humans can specifically respond to about 10 million different antigens due to this diversity.

Question 19

What is immunological memory, and how does it develop?

Answer 19

Immunological memory is developed after the immune system responds to a pathogen for the first time, and it “remembers” the pathogen for future responses. This memory allows for a quicker and more powerful response if the pathogen invades again. Vaccination introduces an antigen to stimulate this memory.

Question 20

What are the two types of specific immune responses?

Answer 20

The specific immune system has two types of responses:

Humoral immune response involves B cells and antibodies (Abs).
Cellular immune response involves cytotoxic T cells.

These responses operate simultaneously and cooperatively, with antigen-presenting cells exposing the antigen to T and B cells and T-helper cells integrating the two responses.

Question 21

How does the humoral immune response work?

Answer 21

in the humoral immune response, antibodies secreted by B cells react with antigens in blood, lymph, and tissue fluids. The B cell has the same specific receptors as the antibodies on its surface. Upon the first invasion by an antigen, it may bind to the B cell, prompting the B cell to make multiple copies of the antibody.

Question 22

What is the cellular immune response?

Answer 22

The cellular immune response detects and destroys virus-infected cells and mutated cells through T cells, which roam in the blood, lymph, and extracellular spaces in tissues. T cell receptors bind to specific antigens, initiating an immune response that results in the destruction of the foreign cell.

Question 23

How is lymphocyte diversity generated?

Answer 23

: Lymphocyte diversity is primarily generated by DNA changes just after B and T cells are formed, during their maturation process. Each B cell is capable of producing only one kind of antibody, and each T cell has specific T cell receptors. This diversity ensures a broad response machinery is present before antigens are encountered.

Question 24

What is clonal selection?

Answer 24

Clonal selection is the process whereby antigen binding selects a B or T cell for proliferation. Binding and activation of a particular lymphocyte result in its proliferation, creating a clone of genetically identical cells that will carry out the immune response.

Question 25

What are the two kinds of daughter cells produced by an activated lymphocyte?

Answer 25

An activated lymphocyte produces two kinds of daughter cells:

Effector cells, which carry out the attack. Effector B cells (plasma cells) secrete antibodies, while effector T cells secrete cytokines.
Memory cells are long-lived and can divide quickly to produce more effector cells upon re-exposure to the antigen.

Question 26

What are the primary and secondary immune responses?

Answer 26

The primary immune response occurs when an antigen is first encountered, leading to the proliferation of naïve lymphocytes into clones of effector and memory cells. The secondary immune response occurs when an antigen is encountered again, and memory cells proliferate

Question 27

How does the body normally tolerate its own molecules, and what is clonal deletion?

Answer 27

: The body is typically tolerant of its own molecules, a trait that develops during the early differentiation of B and T cells. This self-tolerance is maintained through a process known as clonal deletion, where any immature B or T cells that have the potential to mount an immune response against the body’s own antigens are eliminated via apoptosis, preventing autoimmunity.

Question 28

How does a B cell develop into a plasma cell?

Answer 28

A B cell develops into a plasma cell if a T-helper (TH) cell with the same specificity also binds to the antigen (Ag). Signals from the TH cell stimulate the division and differentiation of the B cell. As the plasma cell develops, the endoplasmic reticulum (ER) and ribosomes increase to enhance the synthesis of antibody (Ab) proteins.

Question 28

What is the structure of antibodies?

Answer 28

Antibodies belong to the class of proteins called immunoglobulins and consist of a tetramer of four polypeptides: two light chains and two heavy chains, held together by disulfide bonds. They have a constant region, which defines the class, function, and destination of the antibody, and variable regions that are specific for each immunoglobulin and responsible for antibody specificity. Antibodies have two antigen-binding sites and are bivalent.

Question 29

What are the classes of antibodies and their roles?

Answer 29

There are five classes of antibodies:

IgG is the most abundant, soluble in blood, lymph, and tissue fluids, and is produced in the greatest amounts during the secondary immune response. Some IgG bind to antigens and then to macrophages, which engulf the antigen.

Question 30

What are monoclonal and polyclonal antibodies?

Answer 30

Monoclonal antibodies are made by identical B cells that are all clones of a single parent cell and can bind to one specific part of an antigen. Polyclonal antibodies are produced by different B cells and can bind to multiple parts of an antigen.

Question 31

What are the uses of monoclonal antibodies?

Answer 31

Monoclonal antibodies are used for immunoassays, to detect small amounts of molecules in tissue or fluids, and for immunotherapy, targeting antigens on the surfaces of cancer cells. They can be coupled with radioactive or toxic ligands for therapeutic purposes.

Question 32

What are the types of effector T cells in the cellular immune response?

Answer 32

The cellular immune response involves two types of effector T cells:

T-helper cells (TH) assist both humoral and cellular responses.
Cytotoxic T cells (TC) detect and destroy virus-infected and mutated cells by lysis.

Question 33

What is the role of Major Histocompatibility Complex (MHC) proteins?

Answer 33

MHC proteins are plasma membrane glycoproteins whose main role is to present antigens to T cell receptors, enabling T cells to distinguish between self and non-self antigens. There are two classes of MHC proteins: Class I MHC, found on every nucleated cell, and Class II MHC, found on surfaces of B cells, macrophages, and other antigen-presenting cells.

Question 34

What happens during the activation and effector phases of the cellular immune response?

Answer 34

During the activation phase, a virus-infected or altered cell displays peptide fragments bound to MHC I, recognized by TC cells, which proliferate. In the effector phase, TC cells produce perforin to lyse target cells and bind to receptors on target cells to initiate apoptosis. TC cells recognize self MHC proteins complexed with foreign or altered fragments.

Question 35

What is the role of regulatory T cells (Tregs)?

Answer 35

Regulatory T cells (Tregs) regulate the immune response by recognizing self antigens. When activated, they release cytokines like interleukin 10, which blocks T cell activation and leads to apoptosis of TC and TH cells bound to the same antigen. Tregs mediate tolerance to self antigens and prevent autoimmune responses.

Question 36

How is antibody diversity generated during B cell development?

Answer 36

During B cell development, antibody diversity is generated through the rearrangement of Ig genes. Each mature B cell produces only one specific antibody with a unique amino acid sequence, thanks to the supergene assembly from smaller gene clusters. This rearrangement involves cutting out and randomly joining one gene from each cluster, while others are deleted, leading to immense diversity.

Question 37

What contributes to the diversity of antibodies?

Answer 37

The diversity of antibodies results from the assembly of two supergenes: one for the light chain and one for the heavy chain, with genes located on separate chromosomes. This process yields about 21 billion possibilities for light and heavy chain diversity combined.

The variable region is the part of the antibody that displays the diversity.

Question 38

What is class switching in B cells?

Answer 38

Class switching in B cells occurs when they change the class of antibody they produce, while maintaining the same antigen specificity. This is achieved through DNA deletions that result in antibodies with different constant regions but the same variable regions. T-helper cells induce class switching through cytokine signals.

Question 39

What are allergic reactions and immediate hypersensitivity?

Answer 39

Allergic reactions are when the immune system overreacts to an antigen that may not be dangerous, producing inflammation and other symptoms. Immediate hypersensitivity involves the production of large amounts of IgE upon allergen exposure, which binds to mast cells and basophils, leading to symptoms like inflammation and difficulty breathing upon re-exposure.

Question 40

How can allergy to pollen be treated through desensitization?

Answer 40

Allergy to pollen can be treated by desensitization, which involves injecting small amounts of the allergen under the skin to stimulate IgG production instead of IgG. Upon the next exposure, IgG binds to the allergen before IgE can, mitigating allergic reactions.

Question 41

What are some examples of autoimmune diseases?

Answer 41

Examples of autoimmune diseases include:

Systemic lupus erythematosus (SLE): Antibodies to cellular components cause inflammation.
Rheumatoid arthritis: Persistent T cell response leads to joint inflammation.
Hashimoto’s thyroiditis: Immune cells attack thyroid tissue.
Insulin-dependent diabetes mellitus (type I): Immune reaction against pancreatic cells that produce insulin, necessitating daily insulin intake.

Question 42

What are immune deficiency disorders?

Answer 42

Immune deficiency disorders can be inherited or acquired, characterized by the absence or malfunction of T or B cells, leading to a compromised defense against pathogens. HIV targets T-helper cells, crucial to both humoral and cellular responses, leading to AIDS.

Question 43

How is HIV transmitted and what is its progression?

Answer 43

HIV is transmitted through bodily fluids containing the virus and infects T-helper cells, macrophages, and antigen-presenting dendritic cells. After an initial immune response, the virus reaches a “set point” level, with the rate of disease progression varying among individuals. Over time, TH cells are destroyed, increasing susceptibility to infections and opportunistic diseases.

Question 44

What are the drug treatments focused on for HIV?

Answer 44

Drug treatments for HIV focus on inhibiting viral proteins to prevent the virus from replicating. These include inhibitors of reverse transcriptase, which catalyzes the synthesis of cDNA from viral RNA, and vital protease, which processes viral proteins into their active forms.