prostate-specific antigen

Examples of prostate-specific antigen in the following topics:

• Prostate Disorders

  • The common prostate disorders are: prostatitis, benign prostatic hyperplasia, high-grade intraepithelial neoplasia, and prostate cancer.
  • The most common prostate disorders are: prostatitis, benign prostatic hyperplasia, high-grade intraepithelial neoplasia, and prostate cancer.
  • For men under 50, the most common prostate problem is prostatitis.
  • Prostatitis is inflammation of the prostate gland.
  • The presence of prostate cancer may be indicated by symptoms, physical examination, prostate-specific antigen (PSA), or biopsy.

• Semen

  • During the process of ejaculation, sperm pass through the ejaculatory ducts and mix with fluids from the seminal vesicle, the prostate, and the bulbourethral glands to form semen.
  • The prostatic secretion, influenced by dihydrotestosterone, is a whitish (sometimes clear), thin fluid containing proteolytic enzymes, citric acid, acid phosphatase, and lipids.
  • After about 15–30 minutes, a prostate-specific antigen present in the semen causes the decoagulation of the seminal coagulum.

• Antigens and Antigen Receptors

  • Note also that antibodies tend to discriminate between the specific molecular structures presented on the surface of the antigen.
  • Therefore, most antigens have the potential to be bound by several distinct antibodies, each of which is specific to a particular epitope.
  • In this case, they are called tumor-specific antigens (TSAs) and, in general, result from a tumor-specific mutation.
  • Antigen(ic) specificity is the ability of the host cells to recognize an antigen specifically as a unique molecular entity and distinguish it from another with exquisite precision.
  • Antigen specificity is due primarily to the side-chain conformations of the antigen.

• Antigenic Determinants and Processing Pathways

  • An epitope, also known as an antigenic determinant, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, and T cells.
  • The latter can use epitopes to distinguish between different antigens, and only binds to their specific antigen.
  • Epitopes determine how antigen binding and antigen presentation occur.
  • This is why polysaccharides are generally T-independent antigens and proteins are generally T-dependent antigens.
  • The determinants need not be located on the exposed surface of the antigen in its original form, since recognition of the determinant by T cells requires that the antigen be first processed by antigen presenting cells.

• Antigen-Presenting Cells

  • Antigen presentation is a process where immune cells capture antigens and then enable their recognition by T-cells.
  • These antigens are different from those in bacteria ("non-self" antigens) or in virally-infected host cells ("missing-self").
  • Unlike B cells, T cells fail to recognize antigens in the absence of antigen presentation, with the important exception of the superantigens.
  • In the upper pathway; foreign protein or antigen (1) is taken up by an antigen-presenting cell (2).
  • In the lower pathway; whole foreign proteins are bound by membrane antibodies (5) and presented to B lymphocytes (6), which process (7) and present antigen on MHC II (8) to a previously activated T helper cell (10), spurring the production of antigen-specific antibodies (9).

• Overview of Adaptive Immunity

  • The adaptive immune system, also known as the specific immune system, is composed of highly-specialized systemic cells and processes that eliminate or prevent pathogenic growth.
  • It provides the body with the ability to recognize and remember specific pathogens through their antigens.
  • The recognition of specific "non-self" antigens in the presence of "self" during the process of antigen presentation
  • The generation of responses that are tailored to maximally eliminate specific pathogens or pathogen-infected cells
  • Helper T cells activate B cells, which proliferate and produce antibodies specific to the antigen, while cytotoxic T cells destroy pathogens that bear the antigen that was presented to them by the APCs.

• Blood Groups and Blood Types

  • If an individual is exposed to a blood group antigen (A or B) that is not recognized as self, the individual can become sensitized to that antigen.
  • This will cause the immune system to make specific antibodies to a particular blood group antigen and form an immunological memory against that antigen.
  • Blood group A individuals have the A antigen on the surface of their RBCs, and blood serum containing IgM antibodies against the B antigen.
  • Blood group B individuals have the B antigen on their surface of their RBCs, and blood serum containing IgM antibodies against the A antigen.
  • Blood group O individuals do not have either A or B antigens on the surface of their RBCs, but their blood serum contains IgM antibodies against both A and B antigens.

• Lymphocytes

  • Subtype 2 helper T cells present antigens to B cells.
  • They are different from NK cells because they only bind to cells that express their specific antigen, and are not large or granular like NK cells.
  • They rapidly proliferate and differentiate into helper and cytotoxic T cells that are specific to that antigen should it be detected in the body again.
  • During antigen presentation, antigen-presenting cells first present antigens to T cells.
  • They are specific to the antigen presented to that BCR and rapidly secrete large amounts of antigen-specific antibodies to prevent reinfection if that antigen is detected again.

• Lymphoid Cells

  • T cells and B cells irecognize specific "non-self" antigens during a process known as antigen presentation with MHC class II (usually done by dendritic cells).
  • Once they have received an antigen, the cells become specifically tailored to eliminate and inhibit the pathogens or pathogen-infected cells that express that antigen.
  • Similar to NK cells, they bind to MHC class I and release granzymes, but will only bind to cells that express their specific antigen.
  • They respond to pathogens by producing large quantities of antigen-specific antibodies which neutralize foreign objects like bacteria and viruses, and opsonize (mark) them to be more easily recognized by other immune cells.
  • The fully differentiated B and T cells are specific to the presented antigen and work to defend the body against pathogens associated with that antigen.

• Clonal Selection and B-Cell Differentiation

  • B cells primarily function to make antibodies against antigens, act as antigen-presenting cells (APCs), and eventually develop into memory B cells to provide long-term immunity.
  • However, B cell recognition of antigens is not the only element necessary for B cell activation.
  • T cell independent activation occurs when antigens directly bind to B cell themselves, usually through cross-linking the antigen to the B cell receptor or receiving the antigen with a toll-like receptor.
  • During B cell clonal expansion, many copies of that B cell are produced that share affinity with and specificity of the same antigen.
  • Clonal selection is a theory stating that B cells express antigen-specific receptors before antigens are ever encountered in the body.