Bone marrow

  • In birds, a lymphoid organ called the "Bursa of fabricius", which is a gut-associatedbone marrow lymphoid tissue, is the primary site of B-cell maturation.
  • In mammals, such as primates and rodents, there is no Bursa, but Bone marrow serve as the "Bursal equivalent", where B-cell maturation occurs.
  • In rabbits, uses gut-associated tissues such as the Appendix as primary lymphoid tissue for important steps in the proliferation and diversification of B-cells.

Popular posts from this blog

B-Lymphocytes

Image
The letter "B" designate from its site of maturation, in the "Bursa of fabricius" in the birds; and " Bone marrow " in the mammalian species, including humans & mice. B-Lymphocytes carries out " Humoral-immune response " by producing antibodies. B-Lymphocytes is stimulated by "T h -lymphocytes". When the antigen stimulate, the B-cell divides repeatedly & differentiate over a 4 to 5 day period, generating a population of Plasma cells & M emory cells. Plasma cells lack membrane-bound antibody, synthesize and secrete one of the five classes of antibody. Each of the approximately 1.5X10 5 molecules of antibody on the membrane of a single B- cell has an identical binding site for antigen. Development of B-Lymphocytes: B-cell differentiation as assessed by membrane immunoglobulin expression can be divided into antigen-independent and antigen-dependent phases. Surrounding microenvironment influences of the bone...
Read more

Granulocytic cells

Image
The granulocytes are classified as Neutrophils, Eosinophils and Basophils on the basis of cellular morphology and cytoplasmic staining characteristics. a) Neutrophils: It has a multi-lobed nucleus & granulated cytoplasm that stains with both acid & basic dyes. It is often called a " Poly-morphonuclear leukocyte' (PMN) These are produced by hematopoiesis in the bone marrow, which are released into the tissues, where they have a life span of only a few days. Movement of circulating neutrophils into tissues called " Extravasation ". The neutrophils contains primary & Secondary granules: Larger, denser primary granules Peroxidase, Lysozyme, Various hydrolytic enzymes Smaller, secondary granules Collagenase, Lactofemn & Lysozyme Both primary & secondary granules are fuse with phagosomes. The cells exhibit a larger " Respiratory Burst " than macrophages & express higher levels of "defensins" than macrophage...
Read more

T-Lymphocytes

Image
The letter " T " designates from its site of maturation, in the " Thymus ".  T-cells regulate the " Cell-mediated immunity ". The cells operates against cells bearing intracellular organisms, T-cells recognize antigen only when it is on the surface of a body cells. T-cells have receptors on their membrane surface (cell markers), which belongs to an important group of molecules known as the “ Major Histocompatibility Complex (MHC)”. There are 4 types of t-lymphocytes are present in immune system. They are : i) T-Helper cells (T H -Cells): The T H -cells recognize and bind to the combination of the antigen with the class -II MHC on the macrophage surface. T H -cells produce a variety of soluble factors known as " Cytokines ". The cytokines induce gamma-interferon" and other "Macrophage activating factors".  The cytokines restore the microbicidal mechanism of the macrophage and bring about the death of the intracellular mi...
Read more