White Blood Cells Overview

Study Notes

WBCs, also known as leukocytes, are formed elements in the blood, distinct from red blood cells and platelets.
They are crucial for immunity, protecting the body from pathogens, foreign particles, and infections.
Unlike red blood cells and platelets, WBCs contain a nucleus.

WBCs originate from multipotent cells in the bone marrow called pluripotent cells.
Hematopoiesis is the process of blood cell production in the bone marrow.
Pluripotent cells differentiate into hematopoietic stem cells (HSCs).
HSCs differentiate through various stages, each with specific cell types:
- Common myeloid progenitor (CMP) produces granulocytes, monocytes, and megakaryocytes.
- Common lymphoid progenitor (CLP) produces lymphocytes.
These progenitors differentiate further into specific WBC types (e.g., neutrophils, eosinophils, basophils, monocytes, lymphocytes).

WBCs are broadly categorized into granulocytes and agranulocytes.
Granulocytes contain granules in their cytoplasm:
- Neutrophils: Most abundant, crucial in the initial response to bacterial infections.
- Eosinophils: Involved in allergic reactions and parasitic infections.
- Basophils: Also involved in allergic reactions, releasing histamine.
Agranulocytes lack visible cytoplasmic granules:
- Monocytes: Phagocytic cells that mature into macrophages.
- Lymphocytes: Crucial in the adaptive immune system, including B cells (produce antibodies), T cells (directly kill infected cells), and natural killer cells.

Blood antigenicity is the potential of substances in blood to elicit an immune response.
Antigens are foreign substances recognized by the immune system.
Misidentification of body antigens can lead to autoimmune disorders.
Blood compatibility testing, crucial in transfusions and organ transplants, is based on this principle.

Platelets are cell fragments, derived from megakaryocytes in the bone marrow.
Essential for blood clotting, preventing excessive bleeding.
Their function involves adhesion, aggregation, and releasing chemicals to induce the coagulation cascade.
Normal platelet count is 130,000 to 400,000 per mm³.

Formation of blood cells from hematopoietic stem cells.
Involves complex steps and cell lineages to generate diverse blood cell types, which are differentiated according to their needs.

A network of specialized cells throughout the body responsible for immune responses and clearing cellular debris.
Primarily composed of macrophages, lymphocytes, and endothelial cells. These cells contribute to phagocytosis, antigen presentation, and inflammatory regulation.