ANATOMY OF THE IMMUNE RESPONSE Concepts The immune

ANATOMY OF THE IMMUNE RESPONSE

Concepts Ø The immune system consists of cells and tissues responsible for protecting the host from invading microbes and self transformed cells. Ø The protection (immunity) is achieved through the existence of several specific and non-specific cells that respond to antigendependent signals. Ø The protection is further strengthened by the strategic distribution of specialized organs throughout the body. These organs are the secondary lymphoid organs, which function as “meeting places” for antigens and the immune cells to interact.

Concepts Ø Immunity is the mechanism of protection. Ø There are two types of Immunity: Ø Innate (natural) Ø Borne with the host Ø non specific Ø Has no memmory Ø Short duration Ø Component: Ø Skin, Muocus memb. , Ø Phagocytic cells, Ø Complement system Ø Plasma proteins Ø Body secretions Adaptive (specific) Inducable Specific Improve on second exposure Long duration protection Lymphocytes

Innate and Adaptive Immune Responses

Lymphatic System

Haematopoiesis Hemotopoeitic Stem Cell (HSC)

Maturation of the Myeloid Cell Lineage

The Cellular Players Polymorphonuclear Leukocytes (PMNs) and Monocytes. Ø ingest antigens and destroy through powerful intracellular mechanisms. Ø PMNs are the first cells to arrive at a site of inflammation. Ø cells die once antigen is removed. Ø monocytes enter sites of inflammation later – differentiate into macrophages and enhance antigen clearance. Natural Killer (NK) Cells Ø large granular lymphocytes. Ø recognize damaged cells through alterations to host cells. Ø kill damaged cells through cytolytic mechanisms.

Primary Lymphoid Organs Ø Sites where cellular components of immunity are generated. Ø Precursor cells are generated in the fetal liver during prenatal development. Ø Precursor cells are generated in the bone marrow postnatally. Ø B lymphocytes (antibody production) mature exclusively in the bone marrow. Ø T lymphocytes (damaged cell recognition) mature in the thymus. Ø Natural killer (NK) cells (damaged cell recognition) mature in the bone marrow. Ø Myeloid cells (APC precursors) mature in the bone marrow.

Structure of the Thymus

Thymocyte Maturation

Secondary Lymphoid Tissues Peripheral Lymph Nodes Ø connected to lymphatic network. Ø drain peripheral tissues – migration of antigen or APCs into the lymph node. Ø compartmentalized to optimize antigen – lymphocyte interactions. Spleen Ø acts as a filter of antigen from the blood. Ø the “white pulp” of the spleen is structurally similar to peripheral lymph nodes. Ø also designed to optimize antigen – lymphocyte interactions.

Peripheral Lymph Node Distribution

Peripheral Lymph Node Structure

Peripheral Lymph Node Structure

Peripheral Lymph Node Structure

Peripheral Lymph Node Structure

Spleen Structure

Spleen Structure

Spleen Structure

Spleen Structure

The Cellular Players Lymphocytes Ø express antigen-specific receptors. Ø mediate effector and regulatory influences. Ø confer long-term immunological memory. Antigen Presenting Cells (APCs) Ø derived (principally) from myeloid lineage. Ø ingest antigens and process them for presentation to lymphocytes within lymphoid tissues. Ø play an important role in determining the quality and quantity of the specific immune response.

Lymphocyte Maturation

Humoral and Cellular Immunity

Mucosal-associated Lymphoid Tissue (MALT)

Mucosal-associated Lymphoid Tissue (MALT)

Cutaneous-associated Lymphoid Tissue

Naïve Lymphocyte Entry into Lymph Nodes

Adhesion Molecule Interactions Between Leukocytes and Endothelial Cells

List of Adhesion Molecules

Initiation of Immune Response

Initiation of Immune Response

Lymphocyte Recirculation

Lymphocyte Recirculation to Peripheral Tissues