L20 Autoimmunity

Question 1

What is immunologic tolerance

Answer 1

State of inability of the competent immune system to mount an immune response against a particular antigen

Question 2

What is self tolerance

Answer 2

Refers to the lack of responsiveness out to an individual zone antigens and it’s underlies her ability to live in harmony with ourselves and tissues

Question 3

What are the two groups of self tolerance

Answer 3

Central tolerance and peripheral tolerance

Question 4

What is central tolerance

Answer 4

Clonal deletion [apoptosis] of auto reactive T & B lymphocytes in the thymus or bone marrow

Question 5

What is peripheral tolerance

Answer 5

Any auto reactive cells that escape central tolerance and migrate to the periphery will be removed or deactivated by
Anergy
Suppression
Deletion
Sequestration

Question 6

Anergy

Answer 6

Irreversible functional inactivation

Question 7

What is suppression

Answer 7

Suppression of auto reactive lymphocytes by regulatory T cells that inhibit their activation

Question 8

What is deletion

Answer 8

Deletion of auto reactive lymphocytes by Apoptosis

Deletion of apoptosis genes leads to development of autoimmune lymphoprliferative disorders

Question 9

Describe antigen sequestration

Answer 9

Certain tissues is brain eye and testis sequester their antigens behind blood tissue barrier to be hidden from auto reactive lymphocytes
traumatic injury may expose these antigens leading to auto immune uveitis or orchitis

Question 10

What are the mechanisms of auto immunity

Answer 10

Failure of self tolerance
genetic factors
infectious factors

Question 11

Describe failure of self tolerance

Answer 11

Inheritance of susibility genes which contribute to the breakdown of self tolerance or regulation of immune responses 

1) breakdown of t cell anergy
2) failure of t cell mediated suppression(AIDS)
3) polyclonal b cell activation
4) release of sequestered self ags and exposure of hidden epitopes through tissue trauma or inflammatory destruction eg: lens crystalline of eye, spermatoza in testis

Question 12

What is polyclonal b cell activation

Answer 12

Several mic organisms and their products are capable of causing polyclonal activation of b cells
some of these simulated lymphocytes may be auto reactive

Question 13

What is The role of susceptibility genes

Answer 13

Defective pathways in HLA alleles
Defective pathways in non HLA genes that regulate central or peripheral tolerance as NOD-2 gene, apoptotic pathways or regulatory t development

Question 14

Auto immune diseases with a familial increase of incidence

Answer 14

Systematic lupus erythematous diabetes mellitus type one and other diseases

Question 15

What is the role of infection

Answer 15

Particularly viral infection through:
Modification of self-antigens
1-costiumlators upregulation
2-molecular mimicry
3-polyclonal b cell activation 

Question 16

Describe co simulators upregulation

Answer 16

Upregulate expression of co simulators on antigen presenting cells resulting in breakdown of anergy and activation of T sells specific for the self antigen

Question 17

Describe molecular mimicry

Answer 17

Where a microbe shares amino acid sequence with a self-antigens then immunological reactions will cross-react the pathogen and become directed against self antigen leading to tissue injury with activation of non-tolerant lymphocytes mediating an auto immune reaction

Question 18

What is the best example of molecular mimicry

Answer 18

Rheumatic heart disease in which antibodies against streptococcal proteins cross react with myocardial proteins and cause myocarditis

Question 19

 describe polyclonal b cell activation

Answer 19

By some viruses
May result in production of auto antibodies leading to tissue injury that may release and structurally modify a self antigence creating non-antigens that are able to activate t cells

Question 20

How can tissue damage an auto immune disease be mediated through hypersensitivity

Answer 20

Type two hypersensitivity reaction example autoimmune hemolytic anemia

Type three hypersensitivity reaction example systematic lupus erthyematosus and rheumatoid arthritis

Type two anti-receptor antibodies example myasthenia gravis

Question 21

What are the general features of auto immune diseases

Answer 21

▪️Cellular or organ specific self antigens
▪️Chronic with relapse is in remission and the damage is often progressive
▪️An individual may have more than one autoimmune disease simultaneously in this place symptoms of multiple diseases
▪️Signs and symptoms presented and the disease itself can be influenced by various other factors such as age hormones and environmental factors
▪️There are several organs that are commonly impacted by autoimmune diseases such as blood vessels, underlying connective tissues joint and muscles red blood cells renal glomerulus skin and endocrine glands such as thyroid or pancreas glands