Diseases of the Immune System, General Pathology

This immunity is also called native immunity, constituting for the first line of defense to pathogens.

Innate immunity

Innate immunity is mediated by:

Cells and molecules that recognize products of microbes and dead cells, which rapidly induces a protective host reaction

This immunity is also known as specific immunity. It consists of mechanisms better stimulated by exposure to microbes and other foreign substances. It develops more slowly but is more powerful in combating infections.

Adaptive immunity

what are the components of innate immunity?

1. Epithelial barriers to block the entry of microbes

2. Defensins on the skin are antimicrobial

3. Phagocytic cells (neutrophils and macrophages)

These cells are specialized cells that are present in the epithelia, lymphoid organs and most tissues. they capture protein antigens and display peptides for recognition by T lymphocytes.

Dendritic cells

These cells are 1 type of ILC that provides early protection against many viruses and intracellular bacteria.

natural killer cells

These cells are lymphocytes that lack T-cell antigen receptors and cannot respond to antigens. They are sources of inflammatory cytokines during early phase of immune reactions.

Innate lymphoid cells (ILCs)

All Toll-like receptors are present in the cell membrane and in endosomal vesicles. They culminate the activation of:

NF-Kappa B that stimulate the synthesis and secretion of cytokines and expression of adhesion molecules. ESSENTIAL IN THE RECRUITMENT OF LEUKOCYTES

These receptors are cytosolic receptors. They recognize a variety of substances released from necrotic or damaged cells (mechanisms are largely unknown):

Nod-like receptors (NLR)

NLR’s signal via cytosolic multi protein complex called the ____, which will activate caspase 1.

inflammasome

these two other receptors are located in the cytosol and detect nucleic acids of viruses. They will stimulate the production of antiviral cytokines.

1. C-type lectin receptors

2. RIG-like receptors

NK' cell’s inhibitory receptors recognize the self class I:

Major Histocompatibility complex

What does NK cells recognize?

1. Injured or abnormal cells such as virus infected cells or tumor cells

2. Surface molecules that are induced by various kinds of stress

What are the two reactions of innate immunity?

1. Inflammation

2. Antiviral defense

What is the mechanism of innate immunity inflammation?

Cytokines and complement proteins are produced during the innate immune reaction and trigger vascular and cellular components of inflammation

What is the mechanism of the antiviral defense in innate immunity?

Type 1 interferons produced in a response to viruses act on infected and uninfected cells and activate enzymes that degrade viral nucleic acids and inhibit viral replication

What are the two types of adaptive immunity?

1. Humoral immunity

2. Cell-mediated immunity

Humoral immunity is mediated by:

B cell lymphocytes (from BM)

Cellular immunity is mediated by:

T cell lymphocytes (thymus)

B cells secrete antibodies known as:

immunoglobulins

B and T cells are present in tissues but will also circulate where?

In the blood vessels and lymphatics, promoting immune surveillance

what is the function of helper T lymphocytes?

Stimulate B lymphocytes to make antibodies and activate other leukocytes to destroy microbes

What is the function of cytotoxic T lymphocytes?

Kill infected cells

What is the function of regulatory T lymphocytes?

Limit the immune response and prevent reactions against self antigens

this receptor is made of a disfulfide linked heterodimer, composed to an alpha and beta polypeptide chain, each having a variable antigen bilding region and constant region.

T-cell Receptor

CD4 and CD8 are expressed onto:

subsets of alpha-beta T cells

What is the function of most CD4 positive T cells?

Cytokines secreting helper cells that assist macrophages and B lymphocytes to combat infections

What is the function of CD8 positive cells?

Destroy cells harboring microbes

What are integrins?

Adhesion molecules to promote the attachment of T cells to antigen presenting cells

The primary lymphoid organs are:

thymus

bone marrow

The secondary lymphoid organs are:

Lymph nodes, spleen, and mucosal and cutaneous lymphoid tissue

These are nodular aggregates of lymphocytes spaced throughout lymph channels in the body

Lymph nodes

What is the role of the spleen in the lymphatic system?

Serves the same role in the immune system response to blood-borne antigens as the lymph nodes do the lymph borne antigens

Where are the cutaneous and mucosal lymphoid systems located?

Under the epithelia of the skin, GI, and respiratory tracts.

What is the function of the cutaneous and mucosal lymphoid systems?

Respond to antigens that entered through breaches in the epithelium

In the human body, the MHC molecules are called:

Human leukocyte antigens (HLA)

Class 1 MHC molecules are expressed on all:

nucleated cells and platelets

Harmful immune reactions are responsible for pathology associated with immunologic diseases, what is this called?

Hypersensitivity

Hypersensitivity reactions can be elicited by:

exogenous environmental antigens

1. pollen

2. food

3. drugs

4. endogenous self antigens

In this hypersensitivity type, injures are mediated by the Th2 cells, IgE antibodies, mast cells, and other leukocytes

Type 1

In type 1 hypersensitivity, mast cells release mediators that:

act on vessels and smooth muscle and pro-inflammatory cytokines that recruit inflammatory cells

In this hypersensitivity type, secreted IgG and IgM antibodies injure cells by promoting their phagocytosis or lysis.

Type 2 (antibody mediated disorders)

In this hypersensitivity type, IgG and IgM antibodies bind antigens in the circulation and the antigen antibody complexes deposit on tissues and induce inflammation.

type 3 (immune complex mediated disorders)

In this hypersensitivity type, T lymphocytes are the cause of injury (TH1 and TH17, CD8 positive CTLs)

Type 4 (cell-mediated immune disorders)

Allergic reactions can be mild or severe, what are some examples?

Rashes or nasal congestion

Fatal (like peanut allergies)

Type 1 hypersensitivity reactions are frequently referred to as:

allergic reactions (antigens are called allergens)

Systemic anaphylaxis is characterized by:

Vascular shock, widespread edema, and difficulty in breathing

What are symptoms of systemic anaphyaxis?

1. itching

2. Hives

3. skin erythema, followed by laryngeal edema, bronchial constriction, vasodilation that can result in shock

what can cause systemic anaphylaxis?

1. Foreign particles

2. Hormones

3. Enzymes

4. Drugs

5. Polysaccharides

6. Environmental exposure (shellfish, peanuts)

Histamine can cause:

intense smooth muscle contraction, vascular permeability, and stimulate mucus secretion

These cells are bone marrow derived cells that are abundant near small blood vessels and nerves in the subepithelial tissues. They contain cytoplasmic membrane bound granules that contain a variety of biologically active mediators.

Mast cells

These mediators are the most potent vasoactive smooth muscle contracting agents known, several times more active than histamine.

Leukotrienes CD4 and D4

What are some clinical examples of antibody mediated (type 2) hypersensitivity?

Transfusion reactions, hemolytic disease of the newborn, autoimmune hemolytic anemia, and certain drug reactions

This is a disease involving multiple organs and is characterized by a vast array of autoantibodies, particularly antinuclear antibodies (ANA)

Systemic lupus erythematosus