This document summarizes and compares the structure and functions of the immune system across different vertebrate classes. It describes that fish rely on regions of lymphoid tissue within organs like the kidney and gut to produce immune cells. In birds, the primary immune tissues are the thymus and bursa of Fabricius, while secondary organs include the spleen, bone marrow, and lymph nodes. Amphibian immune systems reorganize during metamorphosis, and reptilian immune function depends on temperature. The mammalian immune system contains many cell types, including B cells, T cells, dendritic cells, and others. The document also lists some congenital defects of the immune system like immunodeficiency, Omenn

1. FUNCTIONS,
COMPARATIVE
STRUCTURES AND
CONGENITAL DEFECTS OF
THE IMMUNE SYSTEM

2. 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.

4. 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

5. 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

6. 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.

7. • 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) .

8. • MAMMALS: the mammalian immune system is made up of many cells.
B Cells
Dendritic Cells
Granulocytes
Innate Lymphoid Cells (ILCs)
Megakaryocytes
Monocytes/Macrophages
Natural Killer (NK) Cells
Platelets
Red Blood Cells (RBCs)
T Cells
Thymocytes

11. 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

12. 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.

13. (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.

14. • Hypersensitivity