BSc Nursing 1st Year Microbiology Nursing Chapter 5 Immunity Question And Answers

Chapter 5 Immunity Question And Answers

Question 1. Difference between active and passive immunity.
Answer:

Question 2. Write a short note on Immunoglobulin (Ig)
Answer:

Immunoglobulin Definition: Immunoglobulins are glycoprotein molecules that are produced by plasma cells in response to an immunogen and which function as antibodies. The immunoglobulins derive their name from the finding that they migrate with globular proteins when antibody-containing serum is placed in an electrical field.

Immunoglobulin classes: The immunoglobulins can be divided into five different classes, based on differences in the amino acid sequences in the constant region of the heavy chains. All immunoglobulins within a given class will have very similar heavy chain constant regions. These differences can be detected by sequence studies or more commonly by serological means (i.e. by the use of antibodies directed to these differences).

IgG – Gamma heavy chains

IgM – Mu heavy chains

IgA – Alpha heavy chains

IgD – Delta heavy chains

IgE – Epsilon heavy chains.

Question 3. WIDAL Test.
Answer:

Introduction Of Widal Test: In 1896 and named after its inventor, Georges-Fernand Widal, is an indirect agglutination test for enteric fever or undulant fever whereby bacteria causing typhoid fever is mixed with a serum containing specific antibodies obtained from an infected individual.

• In cases of Salmonella infection, it is a demonstration of the presence of O-soma false positive result. Test results need to be interpreted carefully to account for any history of enteric fever, typhoid vaccination, and the general level of antibodies in the populations in endemic areas of the world.
• Widal test is a serological test that is done for the diagnosis of typhoid fever caused by the Salmonella organism. This test detects the “O” and “H” antigens of Salmonella typhi and paratyphi A, B, and C. When facilities for culturing are not available, the Widal test is reliable and can be of value in the diagnosis of typhoid fevers in endemic areas.

WIDAL Test Clinical significance: Typhoid fever or enteric fever occurs when S. Typhi, S. Paratyphi A, S. Paratyphi B, and S. Paratyphi C infect the human body. The body responds to this antigenic stimulus by producing antibodies whose titer rise slowly in the early stages, to a maximum, and then slowly falls till it is undetectable.

Persons with typhoid fever carry the bacteria in their bloodstream and intestinal tract. Transmitted through the ingestion of food or drink contaminated by the feces or urine of infected people

Question 4. ELISA Test.
Answer:

Enzyme-linked Immunosorbent Assay (ELISA): Enzyme-linked immunosorbent assay, commonly known as ELISA or EIA), is similar in principle to RIA but the radioactive tag used in RIA techniques can be replaced with an enzyme. When this enzyme is linked to an antibody and used to detect and measure other antibodies or antigens, the assay is called the enzyme-linked immunosorbent assay (ELISA).

An enzyme conjugated with an antibody reacts with a colorless substrate to generate a colored reaction product. Such a substrate is called a chromogenic substrate. Enzyme-linked immune sorbent assay is a highly sensitive, highly specific, and less expensive technique used in serology to detect antigens or antibodies.

Types of ELISA

1. Indirect ELISA
2. Sandwich ELISA
   • Single antibody or direct sandwich ELISA
   • Double-antibody or indirect sandwich ELISA
3. Competitive ELISA

Uses Of Elisa: ELISA is a simple and versatile technique. It needs only microliter quantities of reactants. ELISA has been used to detect antigens and antibodies of various microorganisms.

Elisa Examples

1. Parasites
   • Entamoeba histolytica antigens in feces
   • Toxoplasma antigens in the patient’s serum.
2. Bacteria
   • Haemophilus influenza antigens in spinal fluid
   • β-hemolytic streptococcal antigen in spinal fluid
   • Labile enterotoxin of E. coli in stools.
   • To detect antibody specific for:
3. Mycoplasmas
   • Chlamydiae
   • Borrelia burgdorferi.
4. Viruses
   • To detect antibody specific for:
   • Hepatitis virus antigens
   • Herpes simplex viruses 1 and 2
   • Respiratory syncytial virus (RSV)
   • Cytomegalovirus

Read And Learn More: Bsc Nursing 1st Year Microbiology Previous year Question and Answers

• • Human immunodeficiency virus (HIV)
  • Rubella virus (both IgG and IgM)
  • Adenovirus antigens—in nasopharyngeal specimens.

Question 5. Difference between Immediate and Delayed Hypersensitivity.
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Question 6. Classify immunoglobulin and write in short about IgG.
Answer:

Immunoglobulin classes: Human serum contains five classes of immunoglobulins—IgG, IgA, IgM, IgD, and IgE in the descending order of the concentration.

Immunoglobulin G (IgG)

1. This is the major immunoglobulin in human serum, accounting for about 80 percent of the total immunoglobulin pool.
2. It has a sedimentation coefficient of 7S and a molecular weight of 150,000.
3. It contains less carbohydrates than other immunoglobulins.
4. The normal serum concentration of IgG is about 8 to 16 mg per ml.
5. It has a half-life of 23 days—the longest of all of the immunoglobulin isotypes.
6. IgG is the predominant immunoglobulin in blood, lymph, peritoneal fluid, and cerebrospinal fluid, and it is distributed nearly equally between extra and intravascular spaces. Therefore, IgG is particularly suitable for passive immunization done by the transfer of serum-containing antibodies (antiserum).
7. Four subclasses of IgG (Ig1, Ig2, Ig3, Ig4) have been recognized. Each subclass possesses a distinct type of γ chain which can be identified with specific antiserum. They constitute about 65 percent, 23 percent, 8 percent, and 4 percent respectively of the total human IgG.
8. Catabolism of IgG is unique in that it varies with its serum concentration. When its level is raised, as in chronic malaria, kala-azar, or myeloma, the IgG synthesized against a particular antigen will be catabolized rapidly and may result in a particular antibody deficiency. Conversely, in hypogammaglobulinemia, the IgG given for treatment will be catabolized only slowly.

Functions of IgG: IgG is a very versatile molecule. It may be considered a general-purpose antibody, protective against those infectious agents which are active in the blood and tissues. It is protective against those microorganisms that are active in blood or tissue.

Question 7. Types of Vaccines.
Answer:

A vaccine [Latin vacca, cow] is a preparation from an infectious agent that is administered to humans and other animals to induce protective immunity against a given disease.

Types of Vaccines

1. Live Vaccines: Live vaccines (for example, BCG, measles, oral polio) are prepared from live (generally attenuated) organisms. These organisms have been passed repeatedly in the laboratory in tissue culture or chick embryos and have lost their capacity to induce full-blown disease but retain their immunogenicity. In general, live vaccines are more potent immunizing agents than killed vaccines.
2. Killed (Inactivated) Vaccines: Organisms killed by heat or chemicals, when infected into the body stimulate active immunity. They are usually safe but generally less efficacious than live vaccines.
3. Toxoids: Certain organisms produce exotoxins, for example, diphtheria, and tetanus bacilli. The toxins produced by these organisms are detoxicated and used in the preparation of vaccines.
4. Cellular Fractions: Vaccines, in certain instances, are prepared from extracted cellular fractions, for example, the meningococcal vaccine from the polysaccharide antigen of the cell wall, the pneumococcal vaccine from the polysaccharide contained in the capsule of the organism and hepatitis B polypeptide vaccines. Although the duration of experience with these vaccines is limited, their efficacy and safety appear to be high.
5. Mixed or Combined Vaccine: If more than one kind of immunizing agent is included in the vaccine, it is called a mixed or combined vaccine. The following are some of the well-known combinations
   1. DPT (Diphtheria-pertussis-tetanus)
   2. DT (Diphtheria-tetanus)
   3. DP (Diphtheria-pertussis)
   4. DPT and typhoid vaccine
   5. MMR (Measles, mumps and rubella)
   6. DPTP (DPT plus inactivated polio).
6. DNA Vaccines: A DNA vaccine elicits protective immunity against a microbial pathogen by activating both branches of the immune system: humoral and cellular. Long-lasting memory are cells also are generated.
   • DNA Vaccines Examples: At present, there are human trials underway with several different DNA vaccines against malaria, AIDS, influenza, hepatitis B, and herpes virus.

Question 8. Explain National immunization scheduled.
Answer:

National Immunization Schedule: The first visit may be made when the infant is 6 weeks old the second and third visits, at intervals of 1 to 2 months. Oral polio vaccine may be given concurrently with DPT. BCG can be given with any of the three doses but the site for the injection should be different. The schedule also covers immunization of women during pregnancy against tetanus. National immunization scheduled.

Question 9. Agglutination.
Answer:

Agglutination: It is an antigen-antibody reaction, in which a particulate antigen combines with its antibody in the presence of electrolytes at an optimal temperature and pH, resulting in visible clumping of particles. It differs from precipitation in which soluble antigen is present in contrast to particulate antigen of agglutination. Principles governing agglutination are the same as that of precipitation.

Agglutination occurs when antigen and antibody are present in optimal proportions. Lattice formation hypothesis holds good for agglutination too. The zone phenomenon may occur when either an antigen or an antibody is in excess.

Types of Agglutination Reaction

1. Slide Agglutination: Test A uniform suspension of antigen is made in a drop of saline on a slide or tile and a drop of the appropriate antiserum is added. Clumping occurs instantly or within seconds when the agglutination test is positive.
   • Slide Agglutination Uses:
     • It is a routine procedure to identify the bacterial trains isolated from clinical specimens. One example is to identify Salmonella species.
     • It is also used for blood group and cross-matching.
2. Tube Agglutination Test: This is a standard quantitative method for determination of antibodies. Serum is diluted serially by doubling dilution in test tubes. An equal volume of a particulate antigen is added to all tubes. The highest dilution of the scrum at which agglutination occurs is antibody titer. Tube agglutination is routinely employed for antibody detection in the diagnosis of Lyphoid (Widal test). brucellosis and typhus fevers (Weil-Felix reaction).

Question 10.Immunoprophylaxis.
Answer:

Medical definition of immunoprophylaxis: the prevention of disease by the production of active or passive immunity. Immunoprophylaxis Protection against infectious diseases by (immunization) acquired by the individual either passively or actively:

1. Passive acquired immunity
2. 2- Active acquired immunity

 

1. Passive acquired immunity
   • Ready-made Ab transferred to individual giving rapid protection and short-lasting immunity: a-Naturally acquired passive immunity Occurs when antibodies are transferred from mother to fetus (IgG ) or in colostrum (Ig A).
   • b- Artificially acquired passive immunity Short-term immunization by injection of
     antibodies, For example: injection of antitoxic serum for treatment of diphtheria or tetanus. – injection of gamma globulin that are not produced by recipient’s cells, to hypogammaglobulin children.
2. Active acquired immunity:
   • An individual actively produces his own Ab. Immunity develops slowly and long-lasting due to the development of immunological memory
   • a-Natural active acquired immunity The person becomes immune as a result of previous exposure to a live pathogen
   • b-Artificially active acquired immunity A vaccine stimulates a primary response against the antigen without causing symptoms of the disease.

Question 11. Difference between oral (OPV) and killed (IPV) Polio vaccine.
Answer:

Question 12. Difference between IgG and IgM.
Answer:

Question 13. Define immunity.
Answer:

Immunity Definition: Immunity Latin immunis, free of burden] refers to the resistance exhibited by the host towards injury caused by microorganisms and their products. Immunity is the capacity of multicellular organisms to resist harmful microorganisms.

Question 14. Classify the immunity types.
Answer:

Immunity Classification: Immunity against infectious diseases is of different types. The discrimination between self and nonself, and the subsequent destruction and removal of foreign material, is accomplished by two arms of the immune system, the innate (or “natural”) immune system, and the adaptive (or “acquired”), specific immune system.

Immunity

1. Innate (or natural) immunity
   1. Nonspecific
      • Species
      • Racial
      • Individual
   2. Specific
      • Species
      • Racial
      • Individual
2. Acquired (or adaptive) immunity
   1. Active
      • Natural
      • Artificial
   2. Passive
      • Natural
      • Artificial

Question 15. Explain the mechanism of innate immunity.
Answer:

Mechanisms of Innate Immunity

1. Epithelial Surfaces
   1. Skin: It not only acts as a mechanical barrier to microorganisms but also provides bactericidal secretions. The high concentration of salt in drying sweat, the sebaceous secretions, and long-chain fatty acids contribute to bactericidal activity.
   2. Respiratory tract: The inhaled particles are arrested in the nasal passages on the moist mucous membrane surfaces. The mucous secretions of the respiratory tract act as a trapping mechanism and hair-like cilia propel the particles toward the pharynx where it is swallowed or coughed out. The cough reflex acts as an important defense mechanism,
   3. Intestinal tract: The mouth possesses saliva which has an inhibitory effect on many micro-organisms. Some bacteria may be swallowed and are destroyed by the acidic pH of gastric juices.
   4. Conjunctiva: Tears have a major role in flushing away bacteria and other dust particles. In addition, lysozyme present in tears has a bactericidal action.
   5. The Genitourinary tract: The flushing action of urine eliminates bacteria from the urethra . The acidic pH of vaginal secretions in females, due to the fermentation of glycogen by lactobacillus (normal flora), renders the vagina free of many pathogens.
2. Antibacterial Substances: Besides specific antibody formation, there are number of nonspecific antibacterial substances present in blood and tissues. These substances are properdin, complement, lysozyme, etc.
3. Cellular Factors: Once the infective agent has crossed the barrier of epithelial surfaces, the tissue factors come into play for defense.)

Question 16. Write a short note on IgM.
Answer:

Immunoglobulin M (IgM)

1. About 10 percent of normal serum Igs consists of this class.
2. It is a heavy molecule (19S; MW 900,000 to 1,000,000 daltons, hence called a ‘millionaire molecule’).
3. The normal serum level of IgM is 1.2 mg/ml.
4. It has a half-life of about 5 days.
5. IgM is the first immunoglobulin to appear after exposure to an antigen.
6. In the circulation, IgM exists as a pentamer of five four-chain units. The five identical IgM monomers are connected to each other by a polypeptide joining the J chain. Polymerization of the subunits depends upon the presence of the J chain as with IgA. Monomeric IgM and IgD are present on the surface of mature, naive B cells.
7. IgM contains 10 Fab fragments, and thus 10 antigen binding sites. Though the theoretical valency is ten, this is observed only with small haptens. The effective valency falls to five with larger antigens, probably due to steric hindrance. Most of IgM (80 percent) is intravascular in distribution.
8. Phylogenetically IgM is the oldest Ig class. IgM is the first class of antibody produced during the primary immune response. It is also the earliest to be synthesized by a fetus beginning by about 20 weeks of age. As it cannot cross the placental barrier, the presence of IgM in the fetus or newborn indicates intrauterine infection. Its detection is, therefore, useful for the diagnosis of congenital infections such as syphilis, rubella, human immunodeficiency virus (HIV) infection, and toxoplasmosis.
9. They are relatively short-lived hence their demonstration in the serum indicates recent infection.
10. Treatment of serum with 0.12 M 2-mercaptoethanol selectively destroys IgM without affecting IgG antibodies. This provides a simple method for differential estimation of IgG and IgM antibodies.
11. Isohemagglutinins (anti-A and anti-B) and antibodies to S. Typhi O antigen and Wassermann reaction antibodies in syphilis are usually IgM.
12. IgM agglutinates bacteria, activates complement by the classical pathway, and enhances the ingestion of pathogens by phagocytic cells. IgM is normally restricted to the intravascular space because of its high molecular weight.