**Question:** Tissue transplanted from one individual to another is called as -

A. Allograft
B. Osteotomy
C. Xenograft
D. Autograft

**Correct Answer:** A. Allograft

**Core Concept:**
Allograft refers to the transplantation of tissues between individuals that do not share a common genetic makeup. In contrast, autograft involves transplantation of tissues from the same individual, xenograft involves transplantation between species of different genetic backgrounds, and osteotomy is a surgical procedure that involves cutting and resetting a bone.

**Why the Correct Answer is Right:**
Allograft transplantation occurs when tissues are taken from one individual with a different genetic makeup and transplanted into another individual. This process is commonly used in reconstructive surgery, orthopedic procedures, and organ transplantation. The immune system recognizes the foreign tissues as "non-self," leading to immune response and rejection. To overcome this, immunosuppressive drugs are often used to suppress the immune system's response.

**Why Each Wrong Option is Incorrect:**

A. Osteotomy: This is a surgical procedure involving the cutting and resetting of a bone. It is a distinct medical procedure and not a type of tissue transplantation.
B. Xenograft: This term refers to the transplantation of tissues between species of different genetic backgrounds, making it incorrect in this context as it involves transplantation between species and not between individuals with different genetic makeup.
C. Autograft: Autograft refers to transplantation of tissues from the same individual, not applicable in this context since the question is about transplantation between individuals with different genetic backgrounds.

**Clinical Pearl:**
Understanding the nuances between these terms is crucial for medical professionals, particularly surgeons, transplant specialists, and immunologists. Allograft transplantation can lead to immune response and rejection, necessitating immunosuppressive therapy, while autograft and xenograft involve different concepts in transplantation.