**Core Concept**
Trastuzumab, commonly known as Herceptin, is a targeted therapy used in the treatment of HER2-positive breast cancer. It works by binding to the HER2 protein on the surface of cancer cells, thereby inhibiting cell growth and inducing apoptosis.

**Why the Correct Answer is Right**
Trastuzumab is a monoclonal antibody produced by recombinant DNA technology, which involves injecting the gene encoding the HER2 antigen into a mouse myeloma cell line. This process allows for the production of antibodies that specifically target the HER2 protein. The resulting antibody is a recombinant humanized monoclonal antibody, meaning it contains both human and mouse components. This humanization is crucial to reducing immunogenicity and increasing the therapeutic window of the drug. By specifically targeting the HER2 protein, trastuzumab is able to selectively bind to and inhibit the growth of HER2-positive breast cancer cells.

**Why Each Wrong Option is Incorrect**
**Option A:** This statement is incorrect because trastuzumab is a recombinant humanized monoclonal antibody, meaning it contains both human and mouse components, not just mouse-derived components.

**Option C:** This statement is incorrect because trastuzumab actually inhibits antibody response by blocking the HER2 protein on the surface of cancer cells, rather than increasing it.

**Option D:** This statement is partially correct in that the protein HER2/Neu is indeed expressed in increased amounts by breast cancer cells, particularly HER2-positive breast cancer cells. However, this option does not specifically address the mechanism of action or production of trastuzumab, making it an incomplete answer.

**Clinical Pearl / High-Yield Fact**
Trastuzumab is a classic example of targeted therapy, which selectively targets specific molecular mechanisms involved in cancer growth and progression. Understanding the mechanism of action and production of trastuzumab is crucial for optimal treatment planning and patient management.

**Correct Answer:**
✓ Correct Answer: B. It is a monoclonal antibody produced by injecting her-2 antigen