22. Which of the following cell types can develop from myeloid lineage?
(A) Macrophages
(B) T lymphocytes
(C) B lymphocytes
(D) Erythrocytes
Cells Derived from the Myeloid Lineage
Introduction
Hematopoiesis is the continuous process by which all blood cells are produced from multipotent hematopoietic stem cells (HSCs) located primarily in the bone marrow. These stem cells possess the remarkable ability to self-renew while also differentiating into every mature blood cell required for oxygen transport, immune defense, blood clotting, and tissue repair. Proper regulation of hematopoiesis is essential for maintaining normal physiological functions throughout life.
During differentiation, hematopoietic stem cells give rise to two major progenitor lineages: the common myeloid progenitor (CMP) and the common lymphoid progenitor (CLP). The myeloid lineage produces erythrocytes, megakaryocytes, platelets, granulocytes, monocytes, macrophages, and several dendritic cell populations. In contrast, the lymphoid lineage produces T lymphocytes, B lymphocytes, natural killer (NK) cells, and certain dendritic cells.
Correct Answer
Correct Options: (A) Macrophages and (D) Erythrocytes
Detailed Explanation
All circulating blood cells originate from hematopoietic stem cells in the bone marrow. One of the earliest developmental decisions is the formation of either the common myeloid progenitor or the common lymphoid progenitor. The myeloid lineage gives rise to several important cell types, including erythrocytes, megakaryocytes, platelets, neutrophils, eosinophils, basophils, monocytes, macrophages, mast cells, and many dendritic cells.
Macrophages develop through the monocyte lineage. Monocytes are produced in the bone marrow from common myeloid progenitors and circulate in the bloodstream before migrating into tissues, where they differentiate into macrophages. These cells perform phagocytosis, antigen presentation, cytokine secretion, tissue remodeling, and immune surveillance.
Erythrocytes, commonly known as red blood cells, also arise from the common myeloid progenitor through erythroid precursor cells. Their primary function is oxygen transport by means of hemoglobin.
In contrast, T lymphocytes and B lymphocytes originate from the common lymphoid progenitor. Although T cells mature in the thymus and B cells mature in the bone marrow, both belong to the lymphoid lineage rather than the myeloid lineage.
Therefore, the correct answers are Options (A) and (D).
Explanation of Each Option
Option (A): Macrophages
This statement is correct. Macrophages develop from monocytes, which originate from the common myeloid progenitor. They function as professional phagocytes and antigen-presenting cells that play essential roles in innate immunity and activation of adaptive immune responses.
Option (B): T Lymphocytes
This statement is incorrect. T lymphocytes arise from the common lymphoid progenitor. They migrate to the thymus for maturation and are responsible for cell-mediated immunity.
Option (C): B Lymphocytes
This statement is incorrect. B lymphocytes also develop from the common lymphoid progenitor and differentiate into plasma cells that produce antibodies during humoral immune responses.
Option (D): Erythrocytes
This statement is correct. Erythrocytes originate from erythroid precursor cells derived from the common myeloid progenitor. Their major function is the transport of oxygen and carbon dioxide throughout the body.
Why Options (A) and (D) are Correct
Both macrophages and erythrocytes are descendants of the common myeloid progenitor. Macrophages develop through the monocyte lineage, whereas erythrocytes arise through erythropoiesis from erythroid precursor cells. Consequently, both belong to the myeloid lineage.
Why the Other Options are Incorrect
Why Option (B) is Incorrect
T lymphocytes belong to the lymphoid lineage and mature in the thymus after originating from common lymphoid progenitor cells.
Why Option (C) is Incorrect
B lymphocytes arise from the lymphoid lineage and are responsible for antibody-mediated immunity rather than myeloid differentiation.
Comparison of All Options
| Option | Cell Type | Origin | Correct or Incorrect |
|---|---|---|---|
| A | Macrophages | Myeloid lineage | Correct |
| B | T Lymphocytes | Lymphoid lineage | Incorrect |
| C | B Lymphocytes | Lymphoid lineage | Incorrect |
| D | Erythrocytes | Myeloid lineage | Correct |
Major Cells Derived from Myeloid and Lymphoid Lineages
| Myeloid Lineage | Lymphoid Lineage |
|---|---|
| Erythrocytes | T Lymphocytes |
| Monocytes | B Lymphocytes |
| Macrophages | Natural Killer Cells |
| Neutrophils | Plasma Cells (from B cells) |
| Eosinophils | Some Dendritic Cells |
| Basophils | |
| Megakaryocytes and Platelets |
Hematopoietic Differentiation Pathway
| Stem Cell | Differentiates Into |
|---|---|
| Hematopoietic Stem Cell | Common Myeloid Progenitor and Common Lymphoid Progenitor |
| Common Myeloid Progenitor | RBCs, Platelets, Granulocytes, Monocytes, Macrophages |
| Common Lymphoid Progenitor | T Cells, B Cells, NK Cells |
Functions of Major Myeloid Cells
| Cell Type | Primary Function |
|---|---|
| Erythrocytes | Transport oxygen and carbon dioxide |
| Macrophages | Phagocytosis and antigen presentation |
| Neutrophils | Destroy bacteria through phagocytosis |
| Eosinophils | Defense against parasites and allergic reactions |
| Basophils | Release histamine during allergic responses |
| Platelets | Blood clotting and wound repair |
Biological Significance of the Myeloid Lineage
The myeloid lineage produces cells that are essential for survival. Erythrocytes transport oxygen to every tissue, platelets prevent excessive blood loss, granulocytes provide rapid defense against pathogens, and macrophages remove microorganisms, dead cells, and tissue debris while also activating adaptive immunity through antigen presentation. Proper regulation of myeloid cell development is therefore essential for maintaining normal immune function, tissue repair, and oxygen transport.
Final Answer
Correct Options: (A) Macrophages and (D) Erythrocytes
Both macrophages and erythrocytes originate from the common myeloid progenitor. In contrast, T lymphocytes and B lymphocytes arise from the common lymphoid progenitor. Therefore, the correct answers are Options (A) and (D).
