Transplantation And Tumor Immunity Question And Answers

Transplantation And Tumor Immunity

Question 1. Write a short note on graft versus-host disease mechanism and its clinical features.
Answer:

When graft mount an immunological response against the antigen of host. This is called as graft versus host disease.

Graft-versus-Host Disease Mechanism

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• After bone marrow transplantation, T cells present in the graft, either as contaminants or intentionally introduced into the host, attack the tissues of the transplant recipient after perceiving host tissues as antigenically foreign.
• The T cells produce an excess of cytokines including TNF-α and interferon-gamma (IFNγ).
• A wide range of host antigens can initiate graft-versus-host disease, among them the human leukocyte antigens (HLA).
• However, graft-versus-host disease can occur even when HLA-identical siblings are the donors.
• HLA-identical siblings or HLA-identical unrelated donors often have genetically different proteins (called minor histocompatibility antigens) that can be presented by major biocompatibility complex molecules to the donor’s
• T-cells which see these antigens as foreign and so mount an immune response.

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Graft-versus-Host Disease Clinical Features 

In acute graft-versus-host disease: This form is seen 1 or 2 weeks after the allogenic bone marrow transplantation is done. Skin lesions appear which are mild rash to diffuse severe sloughing. There is also presence of diarrhea, nausea, vomiting, abdominal pain, liver dysfunction. In chronic graft-versus-host disease: It develops after the 3 months. Skin lesions appear as that of lichen plans.

Question 2. Write briefly on immune response against tumors.
Answer:

Following is the immune response against the tumors

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Specific Immune Response:

• Primary immune response to tumor is cell mediated.
• An important role is played by T cells in destruction of tumor cells.
• Neoplastic cells shed the antigens which are presented to T cells by macrophages.
• T cells which are abiogenically stimulated release lymphokines.
• Activated T-lymphocytes cooperate to B-cells and activate them to produce antibodies. These antibodies play an important role in destruction of tumor cells.
• Both activated T-cells and specific antibodies have cytostatic or cytolytic activity.

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Destruction of Tumor Cells

• T-cells have cytotoxic activity and so they help in destruction of tumor cells.
• T-cells also have antibody dependent cell cytotoxicity and with help of antitumor antibody and lymphokine mediated activity they lead to the destruction of tumor cells.

Non-specifi Immune Response

• Both activated macrophages and the natural killer cells non-specifially destroy the tumor cells.
• Armed macrophages bind non-specifially by IgG or IgM antibody by Fc receptor and become non-specifically activated against tumor cell and produce cytolytic effect, i.e. destroy the tumor cell.