Lector Tvorko M. S.

Indication for an assessment of immune status.Indication for an assessment of immune status. 1. Detailed examination of the human health.

2. Genetic defects of the immune system (primary immunodeficiency).

3. Acute and chronic bacterial, viral and protozoan disease (hepatitis, sepsis, chronic pneumonia, leishmaniasis, AIDS etc.).

4. Autoimmune diseases (rheumatism, rheumatoid arthritis, systemic lupus erythematous, etc).

5. Dermatoveneral diseases (contact dermatitis, pemphigus, mycosis fungoides, syphilis, etc.).

6. Tuberculosis and leprosy.

7. Allergic diseases (bronchial asthma, atopy, etc.).

8. Malignant tumours (leukosis, lymphogranulomatosis, lymphosarcoma etc.).

9. Psychical diseases (narcomania, schizophrenia, etc.).

10. Examination of the patients in gerontological and endocrinological hospitals.

11. The control of cytostatic, immunosuppressive and immunostimu- lation therapy.

12. Examination of the recipients before and after transplantations.

The first level tests for assessment of immune status The first level tests for assessment of immune status (approximate): (approximate):

1. Determination of total quantity of lymphocytes in peripheral blood (absolute and relative);

2. Determination of Т– and B–lymphocytes in peripheral blood;

3. Determination of the concentration of the main classes of immunoglobulins;

4. Determination of phagocytic activity of leukocytes.

The second level tests for assessment of immune status The second level tests for assessment of immune status (analytical):(analytical): 1. Determination of subpopulations of T lymphocytes (CD4+ and CD8+);2. Leukocyte migration inhibition test;3. Examination of proliferative ability of T– and B–lymphocytes (lymphocyte blast transformation test);4. Cutaneous tests of hypersensitivity;5. Determination of circulating immune complexes; 6. Determination of B-lymphocytes which carry superficial immunoglobulins;7. Assessment of immunoglobulins synthesis in B-lymphocytes culture;8. Assessment of activity of K–cells and NK–cells; 9. Examination of the components of the complement system;10. Assessment of different stages of phagocytosis.

Immunodeficiency diseases

SCID: severe combined immunodeficiency

Thymic aplasia: DiGeorge anomaly XLA: Bruton’s agammaglobulinemia Common variable immunodeficiency Selective IgA deficiency Wiskott-Aldrich syndrome Ataxia-telangiectasia Chronic granulomatous disease Chédiak-Higashi syndrome Hyper-IgE syndrome (Job’s syndrome)

IMMUNODEFICIENCIESIMMUNODEFICIENCIES Immunodeficiency can occur in any of the four major components of theimmune system: (1) B cells (antibody), (2) T cells, (3) complement, and (4) phagocytes. The deficiencies can be either congenital or acquired.

CONGENITAL IMUNODEFICIENCIESCONGENITAL IMUNODEFICIENCIES

B Cell Deficiencies A. X-Linked Hypogammaglobulinemia (Bruton's Agammaglobuline-mia): Very low levels of all immunoglobulins (IgG, IgA, IgM, IgD, and IgE) and a virtual absence of B cells are found in young boys; f emalecarriers are immunologically normal. Pre-B cells are present, but they fail to differentiate into B cells. B. Selective Immunoglobulin Deficiencies: IgA deficiency is the mostcommon of these; IgG and IgM deficiencies are rarer. Patients with a defi ciency of IgA typically have recurrent sinus and lung infections. The cause of IgA deficiency may be a failure of heavy-chain gene switching. Patients with selective IgM deficiency or deficiency of one or more of the IgG subclasses also have recurrent sine-pulmonary infections caused by pyogenic bacteria such as S. pneumoniae, H. influenzae, or S. aureus.

T Cell DeficienciesT Cell Deficiencies

A. Thymic Aplasia (DiGeorge's Syndrome). Severe viral, fungal, or protozoal infections occur in affected infants early in life. a result of a profound deficit of T cells. Both the thymus and the parathyroids fail to develop properly. The most common presenting symptom is tetany due to hypocalcemia caused by hypoparathyroidism. Other congenital abnormalities are common. A transplant of fetal thymus may reconstitute T cell immunity.

Combined B Cell and T Cell DeficienciesCombined B Cell and T Cell Deficiencies

A. Severe Combined Immunodeficiency Disease (SCID): Recurrent infections caused by bacteria, viruses, fungi, and protozoa occur in early infancy (3 months of age), because both B cells and T cells are defective.

This is a group of inherited diseases, all of which are due to a defect in the differentiation of an early stem cell.

B. Wiskott-Aldrich Syndrome: Recurrent pyogenic infections, eczema, and bleeding caused by thrombocytopenia characterize this syndrome. These symptoms typically appear during the first year of life. The defect appears to be in the ability of T cells to provide help to B cells.

C. Ataxia-Telangiectasia: In this disease, ataxia, telangiectasia and curerrent infections appear by 2 years of age. It is an autosomal recessive disease caused by mutations in the genes that encode DNA repair enzymes.

Complement DeficienciesComplement DeficienciesHereditary Angloedema: This is an uncommon autosomal dominant

disease caused by a deficiency of Cl inhibitor. Recurrent Infections: Patients with deficiencies in Cl, C3 or C5 or the

later components C6, C7, or C8 have an increased susceptibility to bacterial infections. Patients with C3 deficiency are particularly susceptible to sepsis with pyogenic bacteria such as S aureus.

Autoimmune Diseases: Patients with C2 and C4 deficiencies have diseases resembling systemic lupus erythematosus.

Phagocyte DeficienciesPhagocyte Deficiencies A. Chronic Granulomatosis Disease (CGD): Patients with this

disease are very susceptible to opportunistic infections with certain bacteria and fungi, eg, S aureus, enteric gram-negative rods, especially Serratia and Burkholderia, and Aspergillus fumigatus. CGD is due to a defect in the intracellular microbicidal activity of neutrophils as a result of a lack of NADPH oxidase activity (or similar enzymes).

B. Chidiak-Higashi Syndrome: In this autosomal recessive disease, recurrent pyogenic infections, caused primarily by staphylococci and streptococci, occur. This is due to the failure of the lysosomes of neitrophils to empty their contents.

ACQUIRED IMMUNODEFICIENCIESACQUIRED IMMUNODEFICIENCIESB Cell DeficienciesB Cell Deficiencies

Common Variable Hypogammaglobulinemia:

T Cell Deficiencies

A. Acquired Immunodeficiency Syndrome:

B. Measles: Patients with measles have a transient suppression of delayed hypersensttivity as manifested by a loss of PPD skin test reactivity.

Complement DeficienciesComplement DeficienciesA. Liver failure: Liver failure caused by alcoholic cirrhosis or by

chronic Hepatitis B or hepatitis C can reduce the synthesis of complement proteins by the liver to a level that severe pyogenic infections can occur.

Neutropenia: Patients with neutropenia present with severe infections caused by pyogenic bacteria such as S aureus and S pneumoniae. Neutrophil counts below 500/μL predispose to these infections. Common causes of neutropenia include cytotoxic drugs

Chronic Fatigue Syndrome (Chronic Fatigue Immune Dysfunction Syndrome)

Immunizations

2 artificial methods to make an individual immune to a disease

Active immunizationadministration of a vaccine so that the patient actively mounts a protective immune response

Passive immunization

individual acquires immunity through the transfer of antibodies formed by an immune individual or animal

The Chinese noticed that children who recovered from smallpox did not contract the disease a second timeYoung children were inoculated with material from a smallpox scab to induce immunity

process known as variolation

Edward Jenner found that protection against smallpox could be induced by inoculation with material from an individual infected with cowpox similar but much

milder disease

Brief history of immunologyBrief history of immunologyRelatively new science; origin

usually attributed to Edward Jenner, but has

deep roots in folk medicineJenner discovered in 1796 that

cowpox (vaccinia) induced protection against

smallpoxJenner called his procedure

“vaccination”

In 1670, Chinese medical practitioners : variolation

It took almost two centuries for smallpox vaccination to become universal

Vaccination enabled the WHO to announce in 1979 that smallpox had been eradicated, arguably the greatest triumph in modern medicine.

Louis Pasteur developed a vaccine against Pasteurella multocida

Practice of transferring protective antibodies was developed when it was discovered that vaccines protected through the action of antibodies

In the 1880s, Louis Pasteur devised a vaccine against cholera in chickens and developed a rabies vaccine that proved a spectacular success upon its first use in a boy bitten by a rabid dog

These practical triumphs led to a search for the mechanisms of protection and the development of the science of immunology

In 1890 Emil von Behring and Shibasaburo Kitasato discovered that the serum of vaccinated individuals contained “antibodies” that specifically bound to the relevant pathogen

3 general types of vaccines

attenuated (live) microbe “treated” to lose virulence but retain antigenicity

killed (inactivated)

Toxoidtoxin treated with heat or formaldehyde to lose toxicity but retain antigenicity

Also called modified live vaccinesUses pathogens that are living but have reduced virulence so they don’t cause disease

Attenuation is the process of reducing virulence

viruses often attenuated by raising them in tissue

culture cells for which they aren’t adapted until

they lose the ability to produce disease bacteria can

be made avirulent by culturing under unusual

conditions or through genetic manipulation

Attenuated Vaccines

Left: A Calmette, centre: a scanning electron micrograph of M tuberculosis, right: a comparison of the efficacy of the BCG vaccines in different populations and areas of the world

How do we make attenuated viruses?

Rubella and Sabin polio vaccines were derived by passage through monkey kidney and duck embryo cells respectively.

Attenuated Vaccines

Can result in mild infections but no disease

Contain replicating microbes that can stimulate a strong immune response due to the large number of antigen molecules

Viral vaccines trigger a cell-mediated immune response dominated by TH1 and cytotoxic T cells

Vaccinated individuals can infect those around them, providing herd immunity

Problems with Attenuated Vaccines

Attenuated microbes may retain enough virulence to cause disease, especially in immunosuppressed individuals

Pregnant women should not receive live vaccines due to the risk of the modified pathogen crossing the placenta

Modified viruses may occasionally revert to wild type or mutate to a virulent form

Inactivated Vaccines

Can be either whole agent vaccines produced with deactivated but whole microbes, or subunit vaccines produced with antigenic fragments of microbes

Both types are safer than live vaccines since they cannot replicate or mutate to a virulent form

When microbes are killed must not alter the antigens responsible for stimulating protective immunity

Formaldehyde is commonly used to inactivate microbes by cross-linking their proteins and nucleic acids

Recognized as exogenous antigens and stimulate a T2H response that promotes antibody-mediated immunity

Problems with Inactivated Vaccines

Do not stimulate herd immunity Whole agent vaccines may stimulate a inflammatory response due to nonantigenic portions of the microbeAntigenically weak since the microbes don’t reproduce and don’t provide many antigenic molecules to stimulate the immune response

Administration in high or multiple doses, or the incorporation of an adjuvant, can make the vaccine more effective

adjuvants are substances that increase the antigenicity of the vaccineadjuvants may also stimulate local inflammationhigh and multiple vaccine doses may produce allergic reactions

General Properties of Attenuated (Live) and Inactivated Vaccines

InactivatedAttenuated (Live)

Virulent pathogen grown under adverse conditions or continued passage through different hosts

Single boost Can be unstable Induces both humoral and

cellular immunity Reversion to virulent form

possible (eg. Sabin vaccine 1 case per 4 million doses)

Contamination with other viruses (eg. SV-40 from Monkey present in Sabin Vaccine)

Inactivation of virulent pathogen by chemicals (formaldehyde) or irradiation with X-rays

Multiple boosts

Stable (important for 3rd world)

Induces primarily humoral immunity

No reversion (provided the inactivation is complete)

Attenuated organisms confer better immunity but are less “safe”

Live attenuatedLive attenuated vaccines are the major class of vaccines for intracellular pathogens. As these agents lead to active infections and propagate in the

body, suitably attenuated strains require low doses of vaccine and lead to a lasting form immunity that is both antibody and cytotoxic. Live attenuated vaccines, therefore, are ideal vaccines if attenuation can be achieved and can be maintained, ie if attenuation is stable and reversion to the virulent

phenotype occurs.

 inactivated   attenuated

cost

higher (greater mass required)

lower (agent replicates in the body)

administration parenteral oral

adjuvant needed not needed

stability good  poor

reversion   absent possible

immunity mucosal immunity absent

antibody-mediated

short-lasting

mucosal immunity present

antibody-mediate and cytotoxic T cells

long-lasting

Toxoid Vaccines

Chemically or thermally modified toxins used to stimulate active immunity

Useful for some bacterial diseases

Stimulate antibody-mediated immunity

Require multiple doses because they possess few antigenic determinants

Modern Vaccine Technology

Research attempts to make vaccines that are more effective, cheaper, and safer

A variety of recombinant DNA techniques can be used to make improved vaccines

Left: in large areas of China hepatitis B has been endemic for a long time leading to high incidences of chronic liver disease and liver cancer. Right: Incidence of human hepatitis in the USA (top) and liver cancer in children in Taiwan (bottom)

DPT vaccine:– Diphtheria: Purified diphtheria toxoid– Pertussis: Acellular fragments of B. pertussis– Tetanus: Purified tetanus toxoid

Meningococcal meningitis: Purified polysaccharide from N. meningitidis

Haemophilus influenzae type b meningitis: Polysaccharides conjugated with protein

Pneumococcal conjugate vaccine: S. pneumoniae antigens conjugated with protein

Principal Vaccines Used in the World to Prevent Bacterial Diseases in

Humans

Smallpox: Live vaccinia virusPoliomyelitis: Inactivated virusRabies: Inactivated virusHepatitis A: Inactivated virusInfluenza: Inactivated or attenuated virusMeasles: Attenuated virusMumps: Attenuated virusRubella: Attenuated virusChickenpox: Attenuated virusHepatitis B: Antigenic fragments (recombinant vaccine)

Principal Vaccines Used in World to Prevent Viral Diseases in Humans