Histology Slides Database: March 2013

Friday, March 1, 2013

What is Graft-vs.-host disease ? & What are the types of Graft vs Host Disease (GVHD) ?

Graft-vs.-host disease is an immune attack on the recipient by cells from a donor

Graft versus host disease (GVHD) occurs when immunologically competent cells are introduced into an immunoincompetent host

The main problem with transplanting organs and tissues is that the recipient host does not recognize the new tissue as its own.

Instead, it attacks it as foreign in the same way it attacks germs, to destroy it.

If immunogenic cells from the donor are transplanted along with the organ or tissue, they will attack the host, causing graft vs. host disease.

The only transplanted tissues that house enough immune cells to cause graft vs. host disease are the blood and the bone marrow

TYPES OF GVHD include :

Acute GVHD occurs within the first 100 days of transplantation and consists of the triad of

–dermatitis,

–enteritis, and

–hepatitis.

Chronic GVHD develops after day 100 and consists of an autoimmune syndrome directed toward multiple organs.

Because the skin often is the earliest organ affected in GVHD, dermatologists are crucial members of the patient's treatment team.

What is the Mechanism of Autoimmune Diseases ?

Failure of peripheral tolerance

–Breakdown of T cell anergy

–Failure of Activation-Induced Cell death

–Failure of T cell Medicated suppression

–Molecular Mimicry

–Polyclonal Lymphocyte Activation

–Release of sequestered Antigens

–Exposure of cryptic self and Epitope Spreading

Genetic Factors in Autoimmunity

Microbial agents in Autoimmunity

What is Immunologic Tolerance ?

Immunologic tolerance is a state in which the individual is incapable of developing an immune response to a specific antigen

Self tolerance refers to lack of responsiveness to an individual’s antigens

In this way it underlies our ability to live in harmony with our own cells and tissues

What is the mechanism of immunologic tolerance ?

1-Central tolerance

Peripheral tolerance

–Clonal deletion by activation induced cell death

–Clonal anergy

–Peripheral suppression by T cells

Histology Slides Database