Exam 3 (THIS) bcells

Function of B Cells

A type of white blood cell that produces antibodies which are proteins that specifically recognize and neutralize foreign substances known as antigens.

Function of T Cells

play various roles in the immune response, including directly killing infected or abnormal cells, activating other immune cells, synthesize cytokines, and regulating immune responses.

Function of B Cells

A type of white blood cell that produces antibodies which are proteins that specifically recognize and neutralize foreign substances known as antigens.

Function of T Cells

play various roles in the immune response, including directly killing infected or abnormal cells, activating other immune cells, synthesize cytokines, and regulating immune responses.

Function of Suppressor T Cells

block the actions of other T cells to prevent an overactive immune response.

Function of Memory T cells

a subset of T cells that "remember" previous encounters with specific antigens. Upon re-exposure to the same antigen, memory T cells mount a faster and stronger immune response, leading to more effective elimination of the pathogen.

• white blood cells that are antigen specific which remain in the body long after an infection has been defeated. If these cells detect the same antigen in the body again they quickly divide and produce antibodies to eliminate the pathogen. 

Helper T cells

activate B cells, macrophages, and killer T cells when there is an infection.

Inflammation Steps

1. Acute phase. The body’s immediate reaction to injury. In this phase swelling is often felt by the individual.

2. Sub acute phase. The phase of injury where the body begins to regenerate.

3. Chronic phase. The phase where the body rebuilds all that was lost or damaged by the injury.

Inflammation Symptoms

Different Parts and Composition of Antibodies

Antibodies (immunoglobulins) consist of four protein chains: two identical heavy chains and two identical light chains. Each chain contains constant regions and variable regions. The variable regions are responsible for antigen recognition, while the constant regions determine the antibody's functional properties.

What does the immune system/response have to have?

must have the ability to recognize and respond to foreign substances (antigens), differentiate between self and non-self, generate specific immune responses, develop immunological memory, and regulate immune reactions to prevent excessive damage to the body's own tissues.

IgG (1/5 Antibodies)

Found in blood and tissues; crosses the placenta; provides long-term immunity; comprises about 75-80% of circulating antibodies.

IgA (2/5 Antibodies)

Found in mucosal secretions (e.g., saliva, tears, breast milk); plays a role in mucosal immunity; around 10-15% of circulating antibodies. 

IgM (3/5 Antibodies)

Initially produced during the primary immune response; found in blood and lymph; activates complement; about 5-10% of circulating antibodies.

IgE (4/5 Antibodies)

Found in small amounts in blood; involved in allergic reactions and defense against parasites; less than 1% of circulating antibodies.

IgD (5/5 Antibodies)

Found on the surface of B cells; functions as a receptor for antigen recognition; exact percentage in circulation is relatively low.

What is an antigen presenting cell and where do you find them?

• They are immune cells that capture, process, and present antigens to T cells, initiating an immune response.

• They are found throughout the body, particularly in tissues involved in immune surveillance such as lymphoid organs, skin, and mucosal surfaces.

What are the different types of fixed macrophages and where do you find them ?

Fixed macrophages are tissue-resident macrophages that remain in specific organs or tissues.

• Kuppfer cells within the liver.

• microglia within the central nervous system.

• alveolar macrophages within the alveolar wall.

• pleural and peritoneal macrophages within serous cavities.

• osteoclast within bone.

• Langerhans cell within the epidermis.

Phagocytosis

1. chemotaxis (migration of phagocytes to the site of infection),

2. adherence (attachment of phagocytes to the pathogen),

3. ingestion (engulfment of the pathogen),

4. digestion (degradation of the pathogen within phagolysosomes)

5. killing or degradation of the organism.

Different Types of White Blood Cells

• neutrophils (phagocytosis),

• eosinophils (defense against parasites and allergic reactions), basophils (release of histamine)

• lymphocytes (adaptive immunity)

• monocytes (differentiate into macrophages).

Natural Killer Cells

are a type of lymphocyte that plays a critical role in the innate immune response. They are found in the blood, spleen, lymph nodes, and other tissues. These cells recognize and kill virus-infected cells, tumor cells, and other abnormal cells without prior sensitization.

Naturally Acquired Active Immunity

occurs when an individual is exposed to a pathogen, either through infection or vaccination, and develops an immune response, leading to long-lasting immunity. 

Naturally acquired passive immunity

occurs when antibodies are transferred from a mother to her offspring across the placenta (in utero) or through breast milk. This type of immunity provides temporary protection to the newborn until its own immune system matures. 

Artificially required active immunity

This type of immunity immunity is induced by vaccination, where the individual is exposed to a weakened or inactivated form of the pathogen, leading to the development of an immune response and long-term immunity.

Artificially required passive immunity

involves the administration of pre-formed antibodies (such as immunoglobulins) obtained from another individual or animal. This provides immediate but temporary protection against specific pathogens.

During the Infectious process, what is the first cell that responds ?

The first cell that responds to infection is often the dendritic cell, which acts as an antigen-presenting cell and initiates the immune response by capturing and processing antigens.

Complement System

a group of proteins that work together to enhance the immune response by promoting inflammation, opsonization (coating of pathogens to facilitate phagocytosis), and direct lysis of target cells.

What is MAC?

MAC (membrane attack complex) is a structure formed by the complement system on the surface of target cells. It creates pores in the cell membrane, leading to cell lysis and death.

Opsonization

the process by which pathogens are coated with molecules (opsonins) that enhance their recognition and phagocytosis by immune cells, such as macrophages and neutrophils.

How does the complement system work

The complement system can be activated through three pathways (classical, lectin, and alternative), leading to the formation of complement proteins that opsonize pathogens, induce inflammation, and form the MAC to lyse target cells.

What are the parts of the antigen and antibody?

Antigens have epitopes or antigenic determinants, which are specific regions recognized by antibodies. Antibodies consist of heavy and light chains, each with variable and constant regions. The variable regions of antibodies bind specifically to antigens.

heavy chain, light chain, constant region, variable region of antibodies

The heavy and light chains make up the basic structure of antibodies. The variable regions of both chains form the antigen-binding site, while the constant regions determine the antibody's class and effector functions.

How are B cells and T cells formed?

Pathogen

a microorganism or agent that causes disease in its host

Antigen

any substance that can be recognized by the immune system and elicits an immune response, typically by binding to antibodies or T cell receptors.

Resistance

refers to the ability of an organism to withstand or fend off infection or disease

Susceptibility

indicating vulnerability to infection or disease.

Pathogenicity

he ability of a microorganism to cause disease in a host

Immunity

the state of protection against infectious agents or other foreign substances.

Pandemic vs. Epidemic

• A pandemic is an outbreak of a disease that occurs over a wide geographic area and affects an exceptionally high proportion of the population.

• An epidemic is a similar outbreak but is confined to a specific region or community.

Difference between nonspecific vs specific resistance

• Nonspecific resistance provides immediate, generalized defense mechanisms against a wide range of pathogens

• while specific resistance involves the recognition of specific antigens and the development of targeted immune responses.

Histamine

involved in allergic reactions and inflammation. It causes vasodilation, increased vascular permeability, and smooth muscle contraction, leading to symptoms such as redness, swelling, and itching.

What do fixed macrophages do?

are tissue-resident macrophages that phagocytose pathogens, present antigens to T cells, and contribute to tissue repair and remodeling. They play a crucial role in innate immunity and immune surveillance.

What do wandering macrophages do?

are circulating monocytes that migrate to tissues in response to inflammation or infection. They differentiate into macrophages upon entering tissues and perform phagocytosis and antigen presentation

CD4 and CD8

CD4 and CD8 are cell surface proteins expressed on T cells.

• CD4 is primarily found on helper T cells, while CD8 is found on cytotoxic T cells. These proteins play a role in T cell activation and function.

How does an antibody bind to an antigen?

Antibodies bind to antigens through interactions between their variable regions and specific antigenic epitopes. This binding is highly specific and enables antibodies to recognize and neutralize pathogens or foreign substances.

How do killer t cells kill and the diff mechanisms

Killer T cells kill target cells through various mechanisms:

- Release of cytotoxic granules containing perforin and granzymes, inducing target cell apoptosis.

- Expression of death receptor ligands (Fas ligand), triggering apoptosis in target cells.

- Secretion of cytokines such as TNF-alpha, promoting inflammation and cell death.

Function of Killer