1	CLSC320 Principles of Immunology Fundamental Concepts in Immunology Program for Clinical Laboratory Science Unit - 02 Stimulators of Immune Response
2	Unit – 02 Guidlines Reading assignment: Pages 38 - 53 of textbook Learning objectives: Those listed on page 39 of textbook Key terms: Those listed on pages 39 & 40 of textbook
3	Definitions Related to Antigens Definitions: 1.Antigen an antigen is any molecule that is capable of inducing an immune response and/or binding with an antibody. 2.Antigenic determinant or epitope the smallest portion of the antigen that is recognized by T and B lymphocytes and also binds with the specific antibody idiotope. 3.idiotope the site on the antibody that is specific for the epitope.
4	Types of Antigens Types of antigens: 1.Proteins 2.Polysaccharides & Lipids 3.Hapten-carrier complex 4.Macromolecules 5.Synthetic 6.Major Histocompatibility Complex (MHC) 7.Thymus-independent 8.Tumor 9.Red Blood Cell Surface
5	Proteins as Antigens Types of antigens: - continued 1.Proteins ˜induces strong humoral and cell-mediated responses ˜produces long-lasting immunologic memory ˜recognition by T lymphocytes is MHC restricted &peptides bound to class I MHC Umainly from intracellular organisms Urecognized by TCR=s of CD8+ cells &peptides bound to class II MHC Umainly from extracellular organisms Uprocessed by antigen-presenting cells UMHC II bound peptides are recognized by TCR=s of CD4+ cells
6	Polysaccharides-Lipids & Haptenes Types of antigens: - continued 2.Polysaccharides and Lipids ˜are not recognized by T cells ˜can not induce cell-mediated immune responses ˜humoral immune response may be induced &mainly IgM produced &short-lived immunity 3.Hapten-Carrier complex ˜haptens are low molecular weight antigens ˜haptens incapable of inducing an immune response by themselves ˜haptens when bound to a larger molecule (carrier molecule) forms a complex that is immunogenic. ˜humoral immune response is induced with Ab=s produced against the hapten alone/carrier alone/or the complex.
7	Macromolecules & Synthetic Antigens Types of antigens: - continued 3.Macromolecules ˜induce a humoral immune response ˜larger than the antigen-binding portion of antibody ˜contains multiple epitopes that will bind with idiotope 4.Synthetic ˜chemically synthesized short peptides ˜sequence of amino acids from known infectious agents ˜act as haptens ˜used as vaccines but limited use due to: Udoes not induce immunologic memory against hapten but rather against carrier molecule
8	MHC Antigens Types of antigens: - continued 5.Major Histocompatibility Complex (MHC) ˜tissue antigens are found on surface of cells: UHLA-A, HLA-B, HLA-C Ualso called alloantigens or class I MHC antigens ˜class II MHC antigens are: UHLA-DR, HLA-DP, and HLA-DQ ˜most polymorphic genes of human genome ˜participate in recognition of self and foreign antigens ˜triggers rejection of incompatible tissue grafts ˜serves as specific tissue markers that reflects genetic makeup of individual
9	Thymus-Independent Antigens Types of antigens: - continued 6.Thymus-independent - no T cell help needed ˜bacterial polysaccharides ˜certain polymerized proteins: ˜appear to stimulate B lymphocytes directly ˜IgM type antibodies only ˜no memory produced ˜current research has found that there is still some T lymphocyte involvement
10	Tumor Antigens - 1 Types of antigens: - continued 7.Tumor ˜immune system can limit the occurrence of tumors ˜certain tumors can evade the immune system ˜malignant tumors consist of a clone of abnormal cells that are derived from normal tissue by mutations in: Uregulatory genes Utumor suppressor genes Uoncogenes genes ˜the abnormal cell clones show loss of: Utheir specific function Utheir biochemical characteristics Utheir normal cell morphology ˜tumor cells may express certain gene products (molecules) called Atumor markers@
11	Tumor Antigens - 2 Types of antigens: - continued 7.Tumor - continued ˜tumor markers may be: U on surface of tumor cells U shed from cells into blood, urine, or other body fluids ˜only a few tumor markers have the ability to stimulate the immune system and are tumor-specific antigens: ˜most tumor markers are expressed by other tumors or even normal cells and are tumor-associated antigens: ˜tumor-associated antigens are useful in: U support of a diagnosis U monitoring progression or regression of tumor U establish prognosis for malignant tumors
12	Tumor Antigens - 3 Types of antigens: - continued 7.Tumor - continued ˜some examples of tumor-specific markers: name of tumor marker type of tumor TdT - cell enzyme CA 125 - cell marker CA 19-9 - cell marker Acute lymphocytic leukemia ovarian tumors pancreatic tumors ˜some examples of tumor-associated markers: name of tumor marker type of tumor CEA AFP B₂M TAG-72 Adult colorectal tumors Liver & testicular tumors Multiple myeloma & inflammation Breast, stomach, colon, lung, & ovarian
13	Tumor Antigens - 4 Types of antigens: - continued 7.Tumor - continued ˜some examples of tissue-specific markers: name of tumor marker type of tumor cell surface markers serum markers gene or chromosome markers CD10 (CALLA) SIg IL 2 receptor B-cell leukemia B-cell leukemia & lymphoma T-cell leukemia PSA hCT (calcitonin) Prostatic tumors Thyroid tumors p53 gene Ph¹ chromosome Colorectal tumors Chronic myelogenous leukemia
14	Red Blood Cell Antigens Types of antigens: - continued 9.Red Blood Cell Surface ˜two most important constituents of red cell membrane: Uglycophorin Uspectrin ˆa glycoprotein - (CHO + protein) ˆcomprise most of the red cell antigens such as: NABO blood group NDuffy blood group ˆthe Rh blood group has only protein ˆa large protein molecule that allows RBC=s to maintain shape
15	Adjuvants Definition: substances that non-specifically enhances an immune response Mechanism of action: ˜increases size of antigenic molecule ˜prolongs the retention of antigen ˜stimulates macrophages and/or lymphocytes Types of adjuvants ˜Freund=s complete adjuvant ˜Freund=s incomplete adjuvant ˜Most common one used in humans is: ˆkilled mycobacterium in H₂O-oil emulsion ˆantigen + H₂O + oil + emulsifying agent ˆantigen + aluminum hydroxide (alum)
16	Antigen Classification - 1 Definition: antigens can be classified according to site of infectivity as: ˜Extracellular (Exogenous) antigen ˆoutside the cell ˆdirectly accessible to immune system ˆactivates humoral immune system ˆeffector molecules (antibodies) bind to and destroy the antigen ˆexamples of organisms are: Nbacteria Nintracellular organisms that exit cells during part of life cycle %malaria %Babesia
17	Antigen Classification - 2 Definition: antigens can be classified according to site of infectivity as: ˜Intracellular (Endogenous) antigen ˆinside the cell ˆnot directly accessible to immune system ˆactivates cell-mediated immune system ˆeffector cells are T_cytotoxic and destroy both the infected cell and the antigen ˆexamples of organisms are: Nviruses HIV, Hepatitis Nintracellular organisms like: %bacteria M. tuberculosis %rickettsia R. rickettsii
18	Immunogenicity Definition: the ability of an antigen to provoke an immune response Factors that determine an antigens immunogenicity are: ˜Genetic composition of host ˜Genetic dissimilarity ˜Accessibility ˜Size of antigenic molecule ˜Structure of antigenic molecule ˜Size of antigenic dose
19	Factors Determining Immunogenicity - 1 Factors that determine an antigens immunogenicity are: (continued) ˜Genetic composition of host ˜Genetic dissimilarity ˜Accessibility ˜Size of antigenic molecule ˆMHC gene makeup ˆantigen must be recognized as being foreign ˆthe greater the phylogenetic distance the greater the antigenicity ˆantigenic epitopes must be available to immune system ˆ> 10,000 molecular weight to be immunogenic ˆmacromolecules (>100,000) are potent immunogens
20	Factors Determining Immunogenicity - 2 Factors that determine an antigens immunogenicity are: (continued) ˜Structure of antigenic molecule ˜Size of antigenic dose ˆthe more complex the structure the more antigenic the molecule ˆsynthetic molecules (teflon) with repeating units are not immunogenic ˆcomplex molecules (aromatic amines like phenylalanine) are more immunogenic ˆoptimal dose varies depending on antigen ˆlarge doses or repeated doses may lead to tolerance ˆlarge doses may inhibit antibody production
21	Antigen Elimination Factors that determine an antigens elimination: ˜Type of immune response ˜Main site of antigen entry ˆhumoral immune response Ueffector molecule is the antibody Uantibody-antigen complexes formed and are removed by the lymphatic system Uantibody binds to antigen (opsonization) and are phagocytized ˆcell-mediated immune response Ueffector cell is the T_cytotoxic lymphocyte Uantigen is destroyed along with infected host cell
22	Sites of Antigen Elimination - 1 Factors that determine an antigens elimination: (continued) ˜Main site of antigen entry ˆCirculatory system Ucarried to spleen UT-cells recognize it as being foreign Uappropriate immune response destroys antigen ˆSkin Uinflammation occurs at site of entry as a result of humoral defense (phagocytosis) Uantigen may be carried to lymph nodes UT-cells recognize it as being foreign
23	Sites of Antigen Elimination - 2 Factors that determine an antigens elimination: (continued) ˜Main site of antigen entry - (Cont=d) ˆGI or Respiratory system Ulymphoid tissue (Peyer=s patches) in mucosa Uhumoral immune response generated Uantibodies destroy antigen Uactivated lymphocytes carried to surrounding lymph nodes Uantigen being carried to surrounding lymph nodes encounter activates lymphocytes
24	Laboratory Detection of Antigen Methods of Detection: ˜Monoclonal antibodies ˆan antibody produced against a specific epitope ˆcan be used to detect antigen in host ˆcan be used to detect antibody to antigen in host ˆused to detect antigens in: Userum Uplasma Ucells ˜Detection of antigen in cells ˆmonoclonal antibody can be tagged with a fluorescent dye which then binds to antigen ˆa fluorescent microscope can then be used to see antigen
25	OSF - 04 On pages 44 - 46AOne Step Further@ presents a more in-depth discussion of the tumor markers. This presentation is contained on a separate slide presentation called A One Step Further #4" The student may call up the slide program OSF-4 later or click on the arrow below to view slides now.
26	Stimulators of Immune Response Press the ESC key to end program
27	One Step Further Tumor Markers OSF - 4 Pages 44 - 46 click to return to main program
28	Tumor Markers - 2 Definition: Tumor markers are expressions of mutated genes, viral genes, or abnormal expressions of normal host genes resulting in the production of a specific protein. First tumor marker identified was: eBence-Jones protein Žconsists of light chains of immunoglobulins Žproduced by transformed B lymphocytes Ž80% of individuals who have multiple myeloma produce these proteins Ž20% of pateints with Chronic Lymphocytic Leukemia (CLL) also form these proteins
29	Tumor Markers - 3 Old Tumor Markers that have been replaced by new ones: OLD MARKER DISEASE NEW MARKER Acid phosphatase Amylase prostate cancer PSA* *PSA = Prostate Specific Antigen pancreatic cancer CA19-9⁺ ⁺CA19-9 = Cancer Antigen 19-9
30	Tumor Markers - 4 Classification of Tumor Markers: eTumor-specific markers eTumor-associated markers eTissue-specific tumor markers Tumor-specific markers: emolecules that are expressed by tumor cells eMay consist of: Žnew antigenic protein Žaltered cellular protein Žabnormal membrane structural antigens eExamples of tumor-specific markers: ŽTerminal Deoxynucleotidyl Transfrase (TdT) ŽCA125 ŽCA19-9
31	Tumor Markers - 5 Tumor-specific markers: continued eExamples of tumor-specific markers: cont=d ŽTerminal Deoxynucleotidyl Transfrase (TdT) a DNA associated enzyme it is present in patients with Acute Lymphoblastic Leukemia (ALL) it is present in patients with non-hodgkin=s lymphoma of lymphoblastic type ŽCA125 associated with ovarian cancer ŽCA19-9 associated with pancreatic cancer currently under investigation for use
32	Tumor Markers - 6 Tumor-associated markers: emolecules that are expressed by different tumors originating from same cell type eBest characterized tumor-associated markers are the oncofetal antigens which are glycoproteins normally produced by embryonic tissue and not normally found at detectable levels in adults Žalpha-fetoprotein (AFP) Žcarcinoembryonic antigen (CEA) eExamples of tumor-associated markers: Žalpha-fetoprotein (AFP) Žcarcinoembryonic antigen (CEA) ŽB₂M ŽTAG-72
33	Tumor Markers - 7 Tumor-associated markers: continued eExamples of tumor-associated markers: cont=d ŽAlpha-fetoprotein (AFP) elevated levels in: hliver cancer hgerm cell tumors hgastric & pancreatic cancer elevated levels in cirrhosis of liver also ŽCarcinoembryonic antigen (CEA) elevated levels in: hliver cancer hcolon cancer hlung cancer hpancreas, bladder, cervical, and prostate cancer useful as screening method for above cancers useful for monitoring therapy in patients with above cancers
34	Tumor Markers - 8 Tumor-associated markers: continued eExamples of tumor-associated markers: cont=d ŽB₂M (Beta₂-microglobulin) elevated levels in: hmultiple myeloma hSystemic Lupus Erythematosus hRheumatoid Arthritis ŽTAG-72 (Tumor-associated antigen) elevated levels in: hbreast cancer hcolon cancer hlung cancer hstomach cancer hovarian cancer ŽB₂M & TAG-72 are currently under investigation
35	Tumor Markers - 9 Tissue-specific tumor markers: emolecules that are characteristic of a particular tissue type and do not induce an immune response since they are self-antigens eExamples of tissue-specific tumor markers: ŽCD-10 ŽsIgs - surface immunoglobulins ŽIL-2 receptors ŽPSA - prostate-specific antigen ŽCalcitonin
36	Tumor Markers - 10 Tissue-specific tumor markers: continued eExamples of tissue-specific tumor markers: cont=d ŽCD-10 or CALLA elevated levels in: hPre-B cell leukemias hLymphoblastic lymphomas of B- cell type ŽsIgs - (surface immunoglobulins) elevated levels in: hmature B-cell leukemias hlymphomas of mature B-cell type ŽIL-2 receptor elevated levels in: hT-cell leukemias ŽCalcitonin elevated levels in: hthyroid cancers
37	Tumor Markers - 11 Tissue-specific tumor markers: continued eExamples of tissue-specific tumor markers: cont=d ŽPSA - prostate-specific antigen elevated levels in: hprostate cancer used as a screening test for prostate cancer used to monitor therapy in diagnosed cases of prostate cancer much controversy as to usefulness and reliability of this marker
38	Tumor Markers - 12 Gene/chromosome markers: eThere are a couple of markers that are used in diagnosis: Žp53 gene: mutated form seen in: hcolorectal cancer ŽPh¹ chromosome also called the Philadelphia chromosome mutated form of chromosome is a translocation from chromosome 22 to chromosome 9 (t9,22) h85% of CML (chronic myelogenous leukemia) patients have this chromosome
39	Tumor Markers - E click to return to main program