You start working with a professor who has recently discovered a new oncogene wh

Question

You start working with a professor who has recently discovered a new oncogene which can cause sarcoma (tumors of fibroblasts) in mice. He has done many experiments to test if the oncogene can transform a normal fibroblast. He found that the gene can immortalize fibroblasts, make them anchorage-independent, and has observed that they lack contact inhibition, when transfected with this oncogene. Now, he wants you to do some invivo experiments (experiments in animals) to see if the oncogene transfected fibroblasts can cause tumors in mice. To do this you buy two different types of mice from the laboratory where they are produced (Jackson laboratories). Jackson lab.s sends you 10 C57Black and 10 BalbC mice. They tell you that C57Black mice are genetically identical but different from BalbC. BalbC are also genetically identical but they are different genetically from C57Black. In your first experiment you obtain fibroblasts from C57Black mice and transfect them with your oncogene. Then you inject your fibroblasts into C57Black and BalbC mice. You observe that the transformed fibroblasts only generate tumors in C57Black mice, while BalbC mice are tumor free! Then you decide to obtain fibroblasts from BalbC mice and you transform them with the oncogene. When you inject these transformed fibroblasts into BalbC mice, they produce tumors but if you inject them into C57Black mice they don't. How can you explain these observations? In other words, what do you think is the mechanism that lies behind these observations? Please explain briefly.

Explanation / Answer

The transfected cells are being differentiated between being self and non-self. Therefore, the host, from whom the fibroblasts originated in each experiment is able to retain the grafted cells, but the other one rejects it by immunological reactions.

Reason-

There is a group of glycopeptides, called the Major Histocompatibility Complex (MHC) which take part in the recognition of biological entities in the body as self/non/self. They are of two classes - MHC class I and MHC Class II. MHC-I is produced in all nucleated cells throughout the body, while MHC-II is produced in certain types of specialized cells called antigen presenting cells. MHC-I bind (not binds, they are a class of several types) to intrecellular degraded materials and engulfed pathogens by macrophases and present on the surface of the cells. MHC-II bind to extracellular foreign metarials, such as bacteria.

When a tissue is grafted from one individual to another individual, these MHC molecules themselves become antigenic and elicit immunological reactions in the recipient, causing a rejection of the graft, which has heppened here.

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