FUNCTIONS, COMPARATIVE

STRUCTURES AND CONGENITAL DEFECTS OF

THE IMMUNE SYSTEM

What is Immune System?

The immune system is a system of many biological structures and processes within an organism that protects against disease.

Why is this system necessary ?

• Protection from pathogens.

• Removal of dead cells.

• Removal of abnormal cells.

COMPARATIVE STRUCTURES OF THE IMMUNE SYSTEM

At this stage, there is no immune system for all the vertebrates. This the stage of the genesis of the immune system

FISH: Immune organs vary by type of fish. In the some, true lymphoid organs are absent. They rely on regions of lymphoid tissue within other organs to produce immune cells. Eg. erythrocytes, macrophages and plasma cells are produced in the anterior kidney and some areas of the gut where granulocytes mature. The Leydig's organ within the walls of their esophagus and a spiral valve in their intestine. These organs house typical immune cells.They also possess an identifiable thymus and a well-developed spleen where various lymphocytes, plasma cells and macrophages develop and are stored in immune areas within mucosal tissues (e.g. in the skin, gills, gut and gonads. Much like the mammalian immune system, teleost erythrocytes, neutrophils and granulocytes are believed to reside in the spleen whereas lymphocytes are the major cell type found in the thymus

BIRDS: The bird's immune system mainly consists of lymphatic vessels and lymphoid tissue. Primary tissues are the thymus, located in the neck along the jugular vein, and the bursa of Fabricius, located adjacent to the cloaca. Secondary lymphatic organs and tissues would be the spleen, bone marrow, mural lymph nodules and lymph nodes. There is also a lymphatic circulatory system of vessels and capillaries that transport lymph fluid through the bird's body and communicate with the blood supply.

• AMPHIBIANS: The immune systems of the larval forms are competent to defend, they are not equivalent to the mature immune systems that develop after metamorphosis. Metamorphosis is a critical time of transition when increased concentrations of MH, principally TH and corticosteroid hormones orchestrate the loss or reorganization of many tissues and organ systems. Immune system reorganization may serve to eliminate unnecessary lymphocytes that could be destructive if they recognized newly emerging adult-specific antigens on the adult tissues. Increased corticosteroids during metamorphosis appear to induce apoptosis of susceptible lymphocytes.

• REPTILES: The immune system of lizards and snakes is influenced by age, nutrition, general health and temperature. In temperate species thymic involution and splenic follicle regression occur seasonally. Antibody production is temperature dependent. The immune system functions most efficiently within a reptile's preferred optimum temperature zone (POTZ) .

• MAMMALS: the mammalian immune system is made up of many cells.

B CellsDendritic CellsGranulocytesInnate Lymphoid Cells (ILCs)MegakaryocytesMonocytes/MacrophagesNatural Killer (NK) CellsPlateletsRed Blood Cells (RBCs)T CellsThymocytes

CONGENITAL DEFECTS OF THE IMMUNE SYSTEM

Immunodeficiency

Immunodeficiency

(or immune

deficiency) is a

state in which

the immune

system's ability to

fight infectious

disease is

compromised or entirely absent

Omenn’s syndrome

Omenn syndrome is an autosomal

recessive severe combined

immunodeficiency associated

with hypomorphic missense mutations in

the recombination activating

genes (RAG1 and RAG2), affecting

circulating levels of both B-cells and T-

cells.

(DGS) is a primary

immunodeficiency, often but not

always, characterized by

cellular (T-cell) deficiency,

characteristic facies, congenital

heart disease and

hypocalcemia. DGS is caused

by abnormal formation of

certain tissues during fetal

development.

• Hypersensitivity