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CLS 1113 Introduction to Clinical Laboratory Practices

CLS 1113 Introduction to Clinical Laboratory Practices. Unit 4 The Lymph System and Immunoglobulins. The Lymph System. Lymphocytes are wholly responsible for the specific immune recognition of pathogens, thus initiating acquired immunity . Lymphocytes make up 20-40% of circulating WBC’s.

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CLS 1113 Introduction to Clinical Laboratory Practices

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  1. CLS 1113Introduction to Clinical Laboratory Practices Unit 4 The Lymph System and Immunoglobulins

  2. The Lymph System Lymphocytes are wholly responsible for the specific immune recognition of pathogens, thus initiating acquired immunity. • Lymphocytes make up 20-40% of circulating WBC’s. • Lymphocytes are derived from bone marrow stem cells • T cells develop in the thymus • B Cells develop in the bone marrow

  3. Primary Lymph Organs Bone Marrow • Main source of hematopoietic cells - antigen independent lymphopoiesis • Largest tissue in the body • B lymphocytes differentiate Thymus • Flat bilobed organ in the chest cavity. • Increases in size until puberty and then atrophies. • T lymphocytes differentiate

  4. Secondary Lymph Organs • The secondary lymph organs include: • Spleen, lymph nodes, tonsils, and the appendix • Upon differentiation the T and B cells migrate to secondary lymph organs: Recirculate • Approx 1-2% total Lymph / hour • Because lymphocytes are very specific for certain antigens, they must circulate to increase the chances of detection. • Antigen dependent lymphopoiesis

  5. Secondary Lymph Organs Spleen • Red Pulp: Culling of senescent red blood cells • White Pulp: Lymphoid tissue filter • Primary Follicle: unstimulated B Cells Lymph Nodes • Serve as central collecting points for lymph fluid from tissues • Filtration: Phagocytosis, antigen processing and generation of B Cell memory • Secondary Follicle: Antigen stimulated proliferating B cells

  6. Secondary Lymph Organs Tonsils • Respond to respiratory and alimentary tract pathogens • Potential site for Antigen contact Appendix • Potential site for Antigen contact

  7. Surface Markers on Lymphs • Lymphocytes express many molecules (proteins) called “Markers” on the cell surface which are used to differentiate cell populations, etc., i.e. B and T cells • Systematic Nomenclature: CD (Cluster of Differentiation) • Groups or Clusters of Monoclonal antibodies that bind to a specific marker.

  8. CD Markers • CD4 is the Marker expressed on T helper cells. T helper cells are very active in our cell mediated immunity. • The HIV virus attaches to the CD4 markers on T cells (route of entry); that is why HIV patients progressively lose their immune function. • CD8 cells are T suppressor cells / cytotoxic T cells. CD8 cells help keep our immune system under control and help fight tumors (cytotoxic). • The CD markers on our white cells change as the cell matures helping us define maturity or age of the cells.

  9. Antibody Structure and Function: Immunoglobulins • When B cells are stimulated by antigen they undergo differentiation and produce Antibodies a.k.a. Immunoglobulins (Ig) • Glycoproteins found in the serum • Five classes with names based on electrophoretic pattern: IgG, IgM, IgA, IgD and IgE • These differ in size, charge, amino acid concentration and carbohydrate content. • Humoral Immunity

  10. Immunoglobulin Structure • All Ig’s are made up of a four chain polypeptide unit: • Two large chains: HEAVY (H) Chains • Two small chains: LIGHT (L) Chains • Two types:  (kappa) and  (lambda) • FAB: Fragment Antigen Binding • Portion of the antibody that binds to the antigen • Fc: Fragment crystalline • Portion of the antibody that remains constant

  11. IgG • 75% of Serum Immunoglobulins • Monomer: 2 Heavy Chains & 2 Light Chains • Cross Placental Barrier • Number of Sub-Classes • Complement Activation • Optimum Temperature • Predominant Ig in SECONDARY immune response • Table 5-1

  12. IgM • 10% of total serum Immunoglobulin • Pentamer • 10 Heavy & 10 Light Chains • Includes also a J (joining) chain • Predominant Ig in Primary immune response • Complement activation • Optimum Temperature • Cross Placental Barrier • Presence on Lymphocyte membrane

  13. Immunoglobulins • IgA • Location- body secretions • Dimer • Contains a secretory component • J Chain • IgE • Low plasma concentration • Bound to basophils and mast cells • Triggers release of histamines

  14. Immunoglobulins • IgD • Complete function unknown • It is speculated that IgD’s play a role in keep in the immune system under control (suppression).

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