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Normally in mammals, if tissue from another individual enters the body, the foreign cells are recognised as 'non-self' by the immune system - VCE - SSCE Biology - Question 5 - 2008 - Paper 1
Question 5
Normally in mammals, if tissue from another individual enters the body, the foreign cells are recognised as 'non-self' by the immune system. The tissue is then rejec... show full transcript
Worked Solution & Example Answer:Normally in mammals, if tissue from another individual enters the body, the foreign cells are recognised as 'non-self' by the immune system - VCE - SSCE Biology - Question 5 - 2008 - Paper 1
Step 1
Which cells of the immune system are initially responsible for recognising non-self cells introduced by an organ transplant?
Answer
The primary cells of the immune system responsible for recognizing non-self cells in an organ transplant are T-helper cells and antigen-presenting cells. These cells play a crucial role in identifying foreign antigens presented by non-self tissues.
Step 2
How do the cells you have named in part i, distinguish between self and non-self cells?
Answer
The cells mentioned in part i have receptors that are capable of detecting self markers and/or non-self antigens. This is due to the presence of unique molecular signatures on the surface of cells, which are recognized by the receptors of T-helper cells and antigen-presenting cells.
Step 3
Describe the process of tissue rejection after recognition of the non-self cells has occurred.
Answer
Once non-self cells are recognized by the immune system, a series of events take place leading to tissue rejection. Initially, T-helper cells activate cytotoxic T cells and B cells. Cytotoxic T cells directly kill the foreign cells by releasing perforin and granzymes, which induce apoptosis. Concurrently, B cells produce antibodies specific to the antigens present on the non-self cells. These antibodies mark the foreign tissue for destruction by other immune cells, leading to inflammation at the transplant site and ultimately rejection of the transplanted tissue.