66&67: Innate and Acquired Immunity

What is the B cell's effector mechanisms?

Antibody secretion

Which lymphocyte specializes in the detection of extracellular pathogens?

B cell

What are the two different progenitor stem cell lines that are produced by the HSC?

Lymphoid Myeloid

What is the first line of defense against microbes?

Macrophages and neutrophils. Microbes are recognized by receptors that identify common features of many pathogens. They play a critical role in controlling infections before adaptive response takes effect.

What is the role of dendritic cells in innate immunity?

The messengers! Immature DCs can take up antigen by both receptor dependent and receptor independent mechanisms to initiate adaptive immunity.

How is antigen collection in the spleen different from lymph nodes?

Spleen collects antigens from the blood whereas lymph nodes collect antigens from epithelium and connective tissue in lymph.

Which lymphocyte specializes in the detection of intracellular pathogens?

T cell

Why is T cell selection more complex than B cell selection?

T cells recognize foreign antigens as peptide fragments bound to membrane bound proteins of the major histocompatibility complex (MHC). Promote survival of T cells that recognize self MHCs and screen out T cells that strongly recognize self antigens.

How are good B cells selected for?

Tested in bone marrow. If it is adherent to a self antigen, it is eliminated. Bad B cells weeded out in bone marrow.

What is lymph and how does it re-enter the circulation?

The absorbed interstitial fluid that flows through the lymphatic capillaries, into the lymph nodes and eventually back into the vena cava.

Why do we need both innate and adaptive immunity?

The innate immune response immediately, and non specifically, contains the infection while the adaptive immune response takes days to become activated to eliminate the infection.

How do cells of the immune system come in contact with pathogens?

Through lymphoid organs.

Where do T cells differentiate?

Thymus

Why do lymphocytes constantly circulate?

To enhance chance that the lymphocyte will encounter the antigen.

What is the function of the neutrophil in innate immunity?

To phagocytize and activate bactericidal mechanisms.

What is the ultimate goal of decorating microbes with antibodies?

To target the microbe for disposal by phagocytes.

What is the function of the peripheral lymphoid organs?

To trap antigen bearing cells, allow initiation of adaptive immune responses, and provide signals to sustain recirculating lymphocytes.

What are the key players in adaptive immunity?

Lymphocytes produced from the common lymphoid progenitor (B cell and T cell).

What are the two types of responses our system can mount?

- Innate (natural, endogenous) - Adaptive (acquired)

What are the three major routes by which antigens come in?

- Lymph - Blood - Mucosa (gut, lung, repro)

What are the two major types of lymphocytes?

- T cells - B cells

What are the three classes of T cells?

- T helper - T cytotoxic - T regulatory

Responses to antigens typically provides protective immunity. Give some examples of when the response is harmful instead of beneficial.

- allergy to innocuous substance - grafted organ rejection - autoimmunity - cancer

What are the three systems that the immune system cells migrate into?

- blood - lymphatic system - peripheral tissues

What are the two central lymphoid organs?

- bone marrow - thymus

What is the function of the spleen?

- collects antigens from blood - collects and disposes of senescent RBCs

What are the three granulocytes involved in parasitic containment?

- eosinophils - basophils - mast cells

Where can more diffuse lymphoid tissue aggregates similar to GALT be found?

- lung (BALT) - nose (NALT)

What are the peripheral (secondary) lymphoid organs?

- lymph nodes - spleen - mucosal lymphoid tissues (peyer's patches, appendix, tonsils)

What is innate immunity?

- non-specific immune response - present in all individuals at all times - immediately available - does not confer protective immunity (no memory)

What are the two major sections of the spleen and what are their functions?

- red pulp: site of RBC destruction. - white pulp: regions of lymphocytes surrounding arterioles.

What is adaptive immunity?

- specific immune response to an antigen - occurs during lifetime as an adaptation to infection - can confer protective immunity - takes time to develop

What are the four main tasks that the immune system performs to protect against disease?

1. Immunological recognition 2. Immune effector function 3. Immune regulation 4. Immunological memory

What are the three key players in innate immunity?

1. macrophage 2. dendritic cell (immature) 3. neutrophil

What are the three main effector mechanisms of secreted antibodies in host defense for B cells?

1. Neutralization (block microbe recognition by host) 2. Opsonization (coat microbe so that it is recognized) 3. Complement activation (direct kill or indirect kill)

What is immunity?

A natural or acquired resistance to an infectious disease caused by: • Viruses • Bacteria • Fungi • Parasites

What happens during the first stages of innate immunity?

Acute inflammation. Bacteria triggers macrophages to release cytokines and chemokines. This is proceeded by vasodilation and increased vascular permeability that causes redness, heat and swelling. Inflammatory cells migrate into tissue, releasing inflammatory mediators that cause pain.

What is the function of dendritic cells in innate immunity?

Although they have phagocitic properties, their main function is to uptake antigen in peripheral sites and activate adaptive immune response.

Where do all of the immune system cells come from?

Bone Marrow

Where do B dells differentiate?

Bone marrow

How is adaptive immunity receptor specificity generated?

By gene recombination events. Genes made up of multiple cassettes. They can combine different cassettes (gene regions located in the b and t cells) gives us diversity.

How are B and T cells differentiated from one another?

By their surface receptors.

How does the action of a cytotoxic T cell differ from a Helper T lymphocyte?

Cytotoxic T lymphocytes recognize intracellular microbes in cells and kill the infected cells. Helper T cells recognize phagocytosed microbes in macrophages and activate macrophages to kill phagocytosed microbes.

What is the Gut-Associated Lymphoid Tissue (GALT)?

Includes tonsils, appendix and Peyer's Patches. It is an aggregation of lymphocytes (bulk of which are B cells) that collect antigens by specialized epithelial cells called M cells.

Which arm of immunity are NK cells considered

Innate

What is the biggest distinction between the antigen receptors in the innate and acquired arms?

Innate recognize a family of molecules while adaptive have a one molecule one receptor system.

What is an antigen?

Molecules that bind to specific receptors on lymphocytes.

What cell in the blood are macrophages derived from?

Monocytes

What are lymphoid organs?

Organized tissues containing large numbers of lymphocytes in a framework of nonlymphoid cells. They are locations where lymphocytes are generated, differentiated, recirculated, and activated by antigens.

what do innate receptors on cells recognize?

Pathogen associated molecular patterns (PAMPS).

What is the function of marcrophages in innate immunity?

Phagocytosis and activation of bactericidal mechanisms as well as antigen presentation.

What do B cells differentiate into?

Plasma cells (antibody secreting)

What are all the cells of the blood derived from (WBCs, RBCs and platelets)?

Pluripotent hematopoietic stem cell

What is the T cell's effector mechanism?

Receptor-mediated recognition and killing of intracellular antigens.

What is an immune response?

The response that we make against infection.

What are lymphatic capillaries and where are they found?

They are found in the skin, epithelia and parenchymal organs to absorb and drain fluid from spaces between tissue cells.

What are some properties of NK cells and what is their function?

They are large lymphocytes with a granular cytoplasm. They lack specific antigen receptors, but release lytic granules that kill some virus-infected cells.

What are some common properties of circulating lymphocytes?

They are small (relative to other WBCs), with condensed chromatin and little cytoplasm. They have very little transcriptional activity.

What do all lymphocytes arise from and where do they differentiate?

They arise from stem cells in the bone marrow and then differentiate in central lymphoid organs.