Stem cells and Immune System Cells AlMustansiriya University

Stem cells and Immune System Cells Al-Mustansiriya University Collage of Pharmacy Lecturer Dr Samah A. Jassam BSc MSc Ph. D MRSB

Stem cells are undifferentiated cells, these cells can divide by mitosis to produce more stem cells (self-renew) cells. They are found in multicellular organisms. Two major types of stem cells in mammals: 1 - Embryonic stem cells, that are isolated from the inner cell mass of blastocytes. 2 - Adult stem cells, which are found in various types of tissues in adult organisms.

The discovery of stem cells • In 1981. the detailed study of the biology of mouse stem cells has led to the discovery of the stem cells. • In 1998, a discovery of a method to derive human stem cells from human embryos and grow the cells in the laboratory. Ethics The embryos used in these studies were created for reproductive purposes through in vitro fertilization procedures. When they were no longer needed for that purpose, they were donated for research with the informed consent of the donor.

Stem cells are recognized from other cell types by three major characteristics as follow: 1. Stem cells are undifferentiated cells. 2. Capable of renewing themselves through cell division, even after long periods of inactivity. 3. They have the potential to become specialized cells, such as muscle cells, blood cells, and brain cells.

Types of Adult Stem Cells Stem cells are classified into two major categories Embryonic stem cells (ESC): these cells are derived from embryos at a developmental stage before the time of implantation would normally occur in the uterus. can give rise to cells from all three embryonic germ layers i. e. ectoderm, mesoderm and endoderm, Adult stem cells (ASC): Adult stem cells are undifferentiated cells found throughout the body that divide to replenish dying cells and regenerate damaged tissue. They are also known as somatic stem cells which can be found in children as well as adults.

Types of Adult Stem Cells 1. Bone marrow hematopoietic stem cells Hematopoietic stem cells are the early precursor cells which give rise to all the blood cell types that includes both the myeloid and lymphoid lineages 2. Bone marrow stromal stem cells: Mammary stem cells provide the source of cells for growth of mammary gland. 3. Neural stem cells: The existence of stem cells in the adult brain following the discovery that the process of neurogenesis 4. Olfactory adult stem cells: Olfactory adult stem cells isolated from human olfactory mucosa cells. 5. Adipose derived adult stem cells: These cell shave also been isolated from human fat tissue.

Present scenario in stem cell therapy 1. 2. 3. 4. Allogenic stem cell therapy: matched or unmatched Syngenic stem cell transplant: Identical twin Autologous stem cell transplant Cord blood stem cell transplant Complications of stem cell therapy 1. infection, 2. regimen toxicity, 3. carcinogenicity, 4. immune deficiency and, 5. mortality due to co-occurrence of complications.

Blood tissue

Structure of Blood tissue is found inside the blood vessels (arteries, arterioles, capillaries, venules and veins). Blood consists of many components (constituents) : • 55% plasma, • 45% which are the blood cells • 99% of the blood cells are red blood cells (erythrocytes) and 1% are the white blood cells (leukocytes) and blood platelets (thrombocytes).

Haematopoiesis is the production of all types of blood cells including formation, development, and differentiation. It occurs in the yolk sack, then in the liver, and lastly in the bone marrow. In the normal situation, haematopoiesis in adults occurs in the bone marrow and lymphatic tissues.

Haematopoietic stem cells (HSCs) HSCs are localised in the medulla of the bone marrow and have the unique ability to give rise to all of the different mature blood cell types and tissues. HSCs are self-renewing cells, some of their daughter cells remain as HSCs, and this phenomenon is called asymmetric division. The other daughter cells will be either myeloid or lymphoid progenitor cells, they can differentiation, but cannot renew themselves.

All blood cells are divided into three lineages • Erythroid cells are the oxygen carrying red blood cells. • Lymphocytes are derived from common lymphoid progenitors. The lymphoid lineage is primarily composed of T-cells and B-cells (types of white blood cells). • Myelocytes, which include granulocytes, megakaryocytes and macrophages and are derived from common myeloid progenitors, are involved in such diverse roles as innate immunity, adaptive immunity, and blood clotting.

Formation of red blood cells (RBC) (erythrocytes) Red blood cell production takes place in the bone marrow under the control of the hormone EPO. This hormone (EPO) is produced in the kidney in response to decreased O 2 delivery (as in anemia and hypoxia). RBC production requires adequate supplies of substrates, mainly iron, vitamin B 12, and folate. RBCs survive about 120 days. They then lose their cell membranes and are largely cleared from the circulation by the phagocytic cells of the spleen, liver, and bone marrow.

Formation of platelets Platelets are produced during haematopoiesis from common myeloid progenitor cells in the bone marrow, which differentiate into promegakaryocytes and then into megakaryocytes. Megakaryocytes stay in the bone marrow and are thought to produce protoplatelets within their cytoplasm, which are released in cytoplasmic extensions upon cytokine stimulus. The protoplatelets then break up into hundreds of platelets that circulate throughout the bloodstream

White blood cells (WBC) (leukocytes) All white blood cells are produced and derived from hematopoietic stem cells in the bone marrow. Leukocytes are found throughout the body, including the blood and lymphatic system. All white blood cells have nuclei, which distinguishes them from the other blood cells. Two pairs of major categories classify them: either by structure into (granulocytes or agranulocytes) or by cell division lineage into (myeloid cells or lymphoid cells).

Maturation of blood cells As a stem cell matures it undergoes changes in gene expression. These changes can often be tracked by monitoring the presence of proteins on the surface of the cell. Leukocytes are rapidly increased during infection. The proliferation and self-renewal of these cells depend on growth factors. It is one of the key players in self-renewal and development of hematopoietic cells is stem cell factor (SCF).