Antigens

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What is the function of the carrier group in an immunogenic substance?

Confer the size (correct)

Provide specificity

Activate immune cells

Enhance antigen-antibody binding

Which component of an antigen molecule is responsible for specificity?

Conferring size

Carrier

Macromolecular protein

Determinants (epitopes) (correct)

How does the difference in structure between a foreign antigen and an animal's own antigen affect the immune response intensity?

It increases the immune response (correct)

It reduces the immune response

It has no impact on the immune response

It weakens the immune response

What are determinants or epitopes of an antigen?

Distinct molecular features Signup and view all the answers

Which cell type specifically binds to determinants or epitopes of an antigen?

T cells Signup and view all the answers

What type of antigens can directly stimulate B cells to produce antibodies without the need for T cell help?

T-independent antigens Signup and view all the answers

What is a characteristic feature of T-independent antigens?

Polymeric structure Signup and view all the answers

Why do T-independent antigens persist for longer periods and continue stimulating the immune system?

They are resistant to degradation Signup and view all the answers

Which property is associated with T-independent antigens that can activate B cell clones specific for other antigens?

Polyclonal activation Signup and view all the answers

What do polysaccharides generally represent in terms of antigenic classification?

T-independent antigens Signup and view all the answers

What distinguishes T-independent antigens from other types of antigens in terms of their immune responses?

Polymeric structure Signup and view all the answers

What is the part of an antibody that recognizes the epitope called?

Paratope Signup and view all the answers

Which type of antigen lacks immunogenicity unless attached to a large carrier molecule?

Haptens Signup and view all the answers

What property do haptens have but lack immunogenicity unless attached to a large carrier?

Antigenicity Signup and view all the answers

Which type of antigens are represented by various natural constituents seen in animals, plants, and microorganisms?

Natural antigens Signup and view all the answers

Complete antigens have both colloidal support (carrier) and __________.

Epitopes Signup and view all the answers

In the context of antigens, what are substances that are non-immunogenic but can react with the products of a specific immune response known as?

Haptens Signup and view all the answers

What is the chemical nature of capsular antigens in most encapsulated bacteria?

Polysaccharidic Signup and view all the answers

What is the role of anticapsular antibodies in an infected animal?

They enhance phagocytosis and intracellular destruction Signup and view all the answers

What is the structure of a virus?

Nucleic acid core surrounded by a protein layer and an envelope containing lipoproteins and glycoproteins Signup and view all the answers

What is the source of endogenous antigens?

Cytoplasmic membrane of mammalian cells Signup and view all the answers

What is the role of the capsule in bacteria?

It protects against phagocytosis and intracellular destruction Signup and view all the answers

What is the role of foreign molecules in food?

They can trigger an immune response and cause an allergic reaction Signup and view all the answers

What type of antigens are characterized by a few copies of many different antigenic determinants?

T-dependent antigens Signup and view all the answers

Which component of the Gram-negative bacterial cell wall is responsible for most of its antigenicity?

Lipopolysaccharide (LPS) Signup and view all the answers

What is the primary chemical nature of flagellar antigens (H antigens) extracted from bacterial flagella?

Protein Signup and view all the answers

How do fimbrial antigens (F antigens) help some Gram-negative bacteria?

By facilitating attachment to cell surfaces Signup and view all the answers

Which component of the Gram-positive bacterial cell wall is involved in the transport of ions across the cell wall?

Lipoteichoic acids Signup and view all the answers

What is the role of pili (sex pili) in bacteria?

Mating and movement Signup and view all the answers

What is the general immunogenicity of proteins?

They are usually very good immunogens Signup and view all the answers

Which type of antigen is usually poorly immunogenic?

Nucleic acids Signup and view all the answers

What makes antigens more easily phagocytosed and generally more immunogenic?

Degradability Signup and view all the answers

Why are lipids generally considered non-immunogenic?

They lack degradability Signup and view all the answers

Which of the following is a characteristic of good immunogens?

Dependence on the degree of foreignness Signup and view all the answers

What distinguishes polysaccharides as good immunogens?

Having a high degree of degradability Signup and view all the answers

What is the role of the determinants (epitopes) in an immunogenic substance?

Providing specificity by being bound by antibodies, B cells, or T cells Signup and view all the answers

What does the carrier group in an immunogenic substance primarily contribute to?

Size and detectability of the molecule Signup and view all the answers

What is the main function of the carrier in an immunogenic substance?

Making the molecule detectable by the immune cells Signup and view all the answers

Which molecules' distinct surface features are capable of being bound specifically by antibodies, B cells, or T cells?

Determinants (epitopes) Signup and view all the answers

In an immunogenic substance, what contributes more to the intensity of the immune response?

Difference in structure between foreign antigens and animal's own antigens Signup and view all the answers

How do capsules protect bacteria?

By overcoming the effects of the capsule Signup and view all the answers

What is the primary chemical nature of bacterial capsular antigens?

Polysaccharidic Signup and view all the answers

What is the role of endogenous antigens presented by MHC I?

Signal to cytotoxic T cells Signup and view all the answers

What triggers an immune response to foreign molecules in food?

Generating allergic reactions Signup and view all the answers

Which type of antigens are represented by the mosaic of protein molecules on mammalian cell membranes?

Nonmicrobial antigens Signup and view all the answers

Why are viruses considered obligate intracellular parasites?

As they require a living host cell for replication Signup and view all the answers

What is a defining property of T-independent antigens?

Polymeric structure with repeated antigenic determinants Signup and view all the answers

How do T-independent antigens differ from other antigens in terms of B cell activation?

T-independent antigens activate B cell clones specific for other antigens Signup and view all the answers

Which cells are directly stimulated by T-independent antigens for antibody production?

B cells Signup and view all the answers

What type of immune response do T-independent antigens generally evoke?

Humoral response Signup and view all the answers

Why do T-independent antigens persist for longer periods within the immune system?

They resist degradation and have repeated antigenic determinants Signup and view all the answers

Which feature distinguishes T-independent antigens from T-dependent antigens?

Ability to activate B cells without T cell help Signup and view all the answers

What type of response occurs when an animal mounts immune responses against normal body components?

Autoimmune responses Signup and view all the answers

Which of the following types of antigens can activate a large fraction of T cells, inducing a cytokine storm?

Superantigens Signup and view all the answers

What is the characteristic of superantigens when compared to conventional T-dependent antigens in terms of T cell activation?

Polyclonal activation of up to 25% of T cells Signup and view all the answers

Which of the following is NOT an example of superantigens associated with certain conditions or microorganisms?

Influenza virus antigens Signup and view all the answers

In superantigenic responses, what fraction of the T cell population can be activated by these antigens?

Up to 25% Signup and view all the answers

What distinguishes superantigens from conventional T-dependent antigens in terms of the immune response they trigger?

Inducing a cytokine storm Signup and view all the answers