Immunology of transplantation and pregnancy

Question 1

Transplantation (Def.)

Answer 1

surgical manipulaton of moving cells, tissues and/or organs from one body to another to replace damaged or absent organs and or/tissues

Question 2

Word for transplantation …

• within same person
• within two subjects of same species
• between different species:

Answer 2

within same person: autograft
within two subjects of same species: allograft
between different species: xenografts

Question 3

Medawars 2 basic principles of transplantation:

Answer 3

1. Graft rejection is due to genetic incompability between donor and recipient
2. the mechanism of rejection is immune

Question 4

Host vs graft reaction

- graft is recognized / rejected by …?

Answer 4

The graft is recognized as nonself by:

1. Tc:
   - recognize nonself MHC molecules (direct recognition)
   - recognize minor histocompatibility antigens (indirect recognition)
2. Antibodies

The graft is rejected by

1. T-cells
2. Lymphokines

! Transplantation immunity is basically cellular!

check scheme!

Question 5

Immune memory in allograft rejection

Answer 5

There is immune memory in allograft rejection, a new tissue is rejected faster

Question 6

Graft vs host disease (GVHD)

- Conditions

Answer 6

Conditions:

• recipient and graft are incompatible (missing MHC molecules in graft)
• graft is composed of live immune cells f.ex. bone marrow, lymphocytes
• immune system of recipient is either supressed f.ex through chemotheraphie or less developed

Question 7

Is GVHD be clinically useful in leukemia patients?

Answer 7

Is GVHD be clinically useful in leukemia patients?
○ leukemia is cancer of white blood cells
○ when transplanting healthy bone marrow, it would attack sick marrow – very helpful

Question 8

Bone marrow transplantation

• use
• different types of transplantation

Answer 8

use:
- used to treat some types of cancer
- chemotherapy and radiotherapy destroy Hematopoietic stem cells (HSCs) - patient needs new bone marrow with undifferentiated lymphoid cells

types:
- auto transplantation: prior to standart therapy, in vitro culturing, reinjection
- allo transplantation of bone marrow
allo transplantation of stem cells

Question 9

Def. Stem cells

Answer 9

• undifferentiated cells within a differentiated tissue

- capacity to renovate and differentiate in all cell types of the tissue of origin

Question 10

Def Embryonic stemm cell

Answer 10

• undifferentiated pluripotent cell originating from the inner cell mass of the blastocyst
• can differentiate into different specialized cell types

Question 11

The paradox of pregnancy

- what kind of graft is the embryo technically and why is it nonetheless tolerated?

Answer 11

The embryo is an allograft

still tolerated because:
1. Avoiding antigen recocnition:
- the embryo occupies a place which is defended by a nonimmunogenic tissue barrier, the trophoblast
trophoblast:
- outer layer of the placenta, encoded by paternal genes
- is does not express MHC molecules – prevents antigenic recognition and thus immune response

2. Change in maternal immune response:
   - predominance of humoral immunity and inhibition of cellular immunity
   - protective effect of MHC-G molecules on trophoblast cells
   - production of immune inhibitors
   - complement inhibition