Vertebrate Immune Cells (Part-I)

Immune System

The body’s defense network that protects against infectious agents, toxins, and damage using various effector cells and molecules that coordinate innate and adaptive immune responses.

Leukocytes (White Blood Cells)

• Cells that perform most immune functions.

• They develop mainly in the bone marrow and circulate in the blood or reside in tissues.

Bone marrow

The primary site where most immune system cells originate, develop, and mature.

Tissue-resident immune cells

• Certain macrophages and lymphocytes

• such as microglia in the central nervous system

• that originate from the yolk sac or fetal liver

• during embryonic development and remain self-renewing throughout life.

Hematopoietic Stem Cells (HSCs)

Stem cells in the bone marrow that give rise to all blood cell types, including immune cells. They are pluripotent, meaning they can differentiate into multiple specialized cells.

Pluripotent Stem Cells

Cells capable of developing into many different cell types, such as red blood cells, platelets, and various immune cells.

Lymphoid lineage

One of the two main developmental lineages of white blood cells that produces lymphocytes, including T cells, B cells, and natural killer (NK) cells.

Myeloid Lineage

The second main developmental lineage of white blood cells that produces monocytes, macrophages, neutrophils, and other related

Lymphatic system

A network of vessels and tissues that drains extracellular fluid and immune cells from tissues, transporting them as lymph, which re-enters the bloodstream.

Lymph

The fluid carried by the lymphatic system that contains immune cells and extracellular fluid, eventually returning to the blood circulation.

Cellular elements of the blood