**Core Concept**
Plasma cells are a type of white blood cell that plays a crucial role in the adaptive immune system. They are responsible for producing and secreting large quantities of antibodies, also known as immunoglobulins, in response to an antigen. This process is essential for neutralizing pathogens and preventing infections.

**Why the Correct Answer is Right**
Plasma cells arise from activated B cells, which undergo a process called clonal expansion and differentiation. During this process, the B cells lose their ability to undergo cell division and instead focus on producing and secreting antibodies. The antibodies produced by plasma cells are highly specific to the antigen that triggered their production, allowing them to bind to and neutralize the pathogen. This process is mediated by the enzyme immunoglobulin light chain (IgLC) and heavy chain (IgHC) assembly, which is responsible for the correct assembly and secretion of antibodies.

**Why Each Wrong Option is Incorrect**
**Option A:** Plasma cells are not responsible for presenting antigens to T cells, which is a function of antigen-presenting cells (APCs) such as dendritic cells and macrophages.

**Option B:** Plasma cells do not produce cytokines, which are signaling molecules produced by immune cells that help to coordinate the immune response. While plasma cells do produce antibodies, they do not produce cytokines like T cells and other immune cells.

**Option C:** Plasma cells are not responsible for phagocytosing pathogens, which is a function of phagocytic cells such as neutrophils and macrophages. Plasma cells focus on producing and secreting antibodies to neutralize pathogens.

**Clinical Pearl / High-Yield Fact**
Plasma cells are a key component of the adaptive immune system, and their dysfunction can lead to immunodeficiency disorders such as multiple myeloma and hypogammaglobulinemia. Understanding the role of plasma cells in antibody production is essential for diagnosing and treating these conditions.

**Correct Answer:** C.