Basic immunology

Define immunity

adaptive process by which a host organism defends itself from attacks by both external and internal agents

Innate immunity

• nonspecific mechanisms

  • barrier and phagocytosis

• inborn defense mechanisms

• Rapid response

Adaptive immunity

• develops in response to infection

• Relies on B and T cells

• Slow to develop but antigen specific

First line of defense

Innate immunity

• Skin

• mucus

• lungs surfactants

• lysozyme

Second line of defense

Phagocytosis by macrophages, neutrophils and mast cells (innate immunity)

Third line of defense

inflammatory response (adaptive immunity)

4 major characteristics of inflammatory response

1. Heat

2. Swelling

3. Redness

4. Pain

Define chemokine and biological activity

subset of cytokines with chemotactic activity which recruits leukocytes, monocytes, eosinophils to site of infection

Primary lymphoid tissues

Bone marrow: B cell maturation

Thymus: T cell maturation

Secondary lymphoid tissues

tissues providing organized sites for antigen, capture, and presentation to cells

• Spleen: first to encounter blood-borne antigens

• all secondary lymphoid tissues are connected by lymphatic vessels EXCEPT spleen

General function of: NK cells

can kill bacterial or viral infected cells, antibody-coated cells, and cells without normal levels of Class 1 MHC

General function of: T-helper cells

Express CD4+ on membrane and controls specific immune responses via antigen presenting cells (APC)

General function of: T-cytotoxic cells

Expresses CD8+ on membrane and can kill virus-infected or abnormal host cells via cytokine IL-2 from helper T cells

• involved in clonal selection

General function of: B- cells

Differentiate into plasma cells which produce antibody

• involved in clonal selection

Define antigen

a forgein substance capable of inducing an immune response

role of cytokines in immunity

characteristics related to antigenicity

• Foreign-ness

• Molecular type (protein > polysaccharide > lipid > nucleic acid)

• Molecular size (larger = more immunogenic)

• composition (heterogeneity increases immunogenicity)

• degradability

define antibody

glycoproteins produced by B-lymphocytes or plasma cells in response to exposure to a particular epitope on a antigen that induced their production

clonal selection in the antibody response by B cells

proliferation of specific B cells after specific immune response

Basic structural unit of the immunoglobulin molecule

• Monomer

• two light chains

• two heavy chains

• disulfide bond

• constant region

• variable region

• hinge region

Function of IgG

• monomer

• memory antibody ( lifelong)

• crosses placenta

Function IgM

• five monomers

• J chain

• produced first

• Transient

Function IgA

• Dimer

• J chain

• secretory component

Function of IgD

• Monomer

• surface marker

• delta heavy chain

Function of IgE

• monomer

• allergic reactions

• espilon heavy chain

classes of immunoglobulins which have J chain

• IgM

• IgA

Primary immune response

• New antigen exposure

• latency window (7-10 days)

• IgM first then IgG but has memory

Secondary immune response

• Antigen seen again

• no latency window

• IgM low then IgG produced immediatelyz and the primary response

role of T cells in humoral immune response

• T-helper cell is activated by antigen

• release cytokines and expressed CD40

• B cells activated and proliferates

How T cells recognize antigen in the cellular immune response

• Cytotoxic T cells need MHC Class 1

  • on all nucleated cells

• allows for differentiation of healthy vs infected/mutated cells

Activities of cytotoxic T cells

• provide a surveillance mechanism

Delayed-type hypersensitivity cells

• controlled by Helper T cells

• Effector cells: macrophage

• type of inflammatory response

4 types of hypersensitivity and their mediator

Type 1

• Mediated by IgE

Type 2

• Mediated by IgG

Type 3

• mediated by immune complexes

Type 4

• cell mediated and delayed

active immunization

uses vaccine or infected to initiate immunity

Passive immunization

uses artificial injections of antibodies from a donor animal into the animal to be immunized or naturally passed in breast milk

process of monoclonal antibody production

fuse of plasma cell with cancerous mouse cells to form a hybridoma

polyclonal antibodies

define complement

complement cascade completion results in lysis of cells

3 major biological activities of the activated complement system

• Release of histamine

• Neutrophil margination, chemotaxis and activation

• Opsonization

Major activator of the Classical and Alternant complement pathways

Classical: Ag/Ab complex

Alternant: bacterial products

Lectin: Mannan-binding lectin

define tolerance

absence of immune response to one’s own antigens

• Tolerance loss: autoimmune disease