36 Questions
What are epitopes?
Small parts of an antigenic molecule that stimulate the specific immune system
Which of the following factors does NOT influence antigenicity?
Climate
What does an adjuvant do?
Prolongs the stimulation of the immune response
Which type of molecule is typically NOT antigenic?
Lipids
What is the consequence of excessive antigen dosage?
Immune suppression
Which of the following is true about haptens?
They require a carrier molecule to become immunogenic
How many different epitopes are present on human albumin, at minimum?
At least six
Which routes of administration of antigens are known to induce a slower but stronger immune response?
Intramuscular routes
Which cells interact with MHC class I molecules?
CD8+ Tc cells
What types of HLA are associated with class II MHC?
HLA-DQ,P,R
On which type of cells are MHC class I molecules found?
All nucleated cells
Which of the following functions is associated with class II MHC molecules?
Stimulates Th cells
Why is the MHC significant in organ transplantation?
Due to graft rejection
Which HLA antigen is associated with ankylosing spondylitis?
HLA-B27
What can result from administering very high or very low doses of certain antigens?
Immunologic tolerance
Why are parental routes preferred over oral routes for antigen administration?
They induce stronger immune responses
What is the role of an adjuvant in vaccination?
Increase the immune response
What is required to stimulate a strong immune response when administering antigens?
Repeated booster doses
What transforms a hapten into an antigenic determinant?
Conjugation to a carrier protein
Which of the following is not typically an example of a hapten?
Alum precipitated toxoid
Which type of MHC molecule is found on all nucleated cells?
Class I
What is the primary role of Class II MHC molecules?
Present antigens to CD4+ helper T cells
Which HLA gene is associated with ankylosing spondylitis?
HLA-B27
Where are the genes that determine histocompatibility antigens located?
On the short arm of chromosome 6
Which class of MHC molecules is involved in the production of complement components?
Class III
Which MHC molecules complex with peptides and present antigens to CD8+ cytotoxic T cells?
Class I
Which region on the short arm of chromosome 6 determines the antigenic specificity of Class II MHC molecules?
Region D
Which of the following cells recognize antigens only when associated with Class II MHC molecules?
CD4+ helper T cells
Which of the following terms is used to describe antibodies directed against an individual's own proteins?
Autoantibodies
What is an important characteristic of the innate immune system?
It is present at birth and always active
What is the role of heterophile antibodies in the Paul Bunnel Test?
To agglutinate sheep or horse RBCs
Which molecule on the surface of most gram-negative bacteria is recognized by the innate immune system?
LPS
What is the main defense function of intact skin and respiratory tract?
Blocking microbial entry
In the context of the immune system, what is known as cross-reactivity?
Antigen binding to an antibody that was produced in response to partially related antigens
What role does the innate immune system play in the adaptive immune response?
Stimulating the adaptive immune response
Which of the following is an in-vivo example of cross-reactivity?
Acute rheumatic fever
Study Notes
Antigens
- Antigens are foreign substances that can stimulate the immune system
- They can be proteins, polysaccharides, lipids, or nucleic acids
- Epitopes or antigenic determinants are specific small parts of the antigenic molecules that can stimulate the immune system
Epitopes or Antigenic Determinants
- The number of epitopes on a molecule varies with molecular size
- For example, human albumin has at least six different epitopes, which means that at least six different antibodies can be produced after immunization
Factors Influencing Antigenicity
- Foreignness: The immune system can distinguish between self and non-self, and only foreign substances can stimulate an immune response
- Molecular size: Small molecules are usually not immunogenic, while larger molecules can be antigenic
- Chemical nature: Proteins are the most potent antigens, while some polysaccharides of high molecular weight can be antigenic
- Methods of administration: The dosage, frequency, and route of administration of antigens can influence the immune response
Adjuvants
- Adjuvants are substances that can enhance the immune response when mixed with an antigen
- Examples of adjuvants include aluminum phosphate, alum precipitated, and diphtheria toxoid
Haptens
- Haptens are substances that are not immunogenic by themselves but can become immunogenic when coupled to a carrier molecule
- Examples of haptens include neomycin, skin ointments, and cosmetics
Types of Antigens
- Bacterial antigens
- Viral antigens
- Human tissue antigens (e.g., blood group antigens, histocompatibility antigens)
Human Tissue Antigens
- Blood group antigens: A and B antigens on red cells, important in blood transfusion reactions
- Histocompatibility antigens: Present on the membrane of tissue cells, also known as major histocompatibility complex (MHC) antigens or human leukocyte antigens (HLA)
Histocompatibility Antigens
- Definition: Molecules present on the membrane of tissue cells that can stimulate an immune response
- Types: Class I, II, and III MHC antigens
- Class I: Present on all nucleated cells
- Class II: Present on antigen-presenting cells (APCs) such as B cells, macrophages, and dendritic cells
- Class III: Involved in the production of complement components
MHC Significance
- Organ transplantation and rejection: MHC antigens play a crucial role in organ transplantation and rejection
- MHC restriction: Th cells recognize peptide antigens on the surface of APCs only when presented with MHC class II molecules, while Tc cells recognize antigens on the surface of virus-infected cells or tumor cells only when presented with MHC class I molecules
- Paternity testing and forensic medicine: MHC antigens can be used to determine paternity and in forensic investigations
- Disease association: Certain MHC antigens are associated with specific diseases, such as HLA-B27 with ankylosing spondylitis and HLA-DR4 with rheumatoid arthritis
Learn about antigens, their composition, and epitopes, the specific parts of antigens that stimulate the immune system.
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