**Question:** Acantolytic cells in pemphigus is-

A. Eosinophils
B. Lymphocytes
C. Neutrophils
D. Plasma cells

**Correct Answer:** D. Plasma cells

**Core Concept:**
Pemphigus is a group of autoimmune diseases characterized by the production of autoantibodies against keratinocyte adhesion molecules, leading to blister formation. In pemphigus, the primary immune cells involved are plasma cells. These plasma cells secrete autoantibodies that target desmoglein proteins, which are key components of desmosomes, adhesion structures between keratinocytes in the epidermis.

**Why the Correct Answer is Right:**
Plasma cells are a type of white blood cells that produce antibodies (immunoglobulins) in response to an antigenic stimulus. In the context of pemphigus, these plasma cells secrete autoantibodies against desmoglein proteins, which are essential for maintaining skin integrity and preventing skin blistering. By targeting these proteins, the autoantibodies disrupt the adhesion between keratinocytes, leading to acantholysis (cell separation) and, subsequently, formation of blisters.

**Why Each Wrong Option is Incorrect:**

A. Eosinophils: While eosinophils are involved in immune responses and inflammation, they are not responsible for the autoantibody production in pemphigus. They are part of the innate immune response and do not play a direct role in the pathogenesis of pemphigus.

B. Lymphocytes: Lymphocytes are another type of white blood cells involved in the adaptive immune response. While they play a role in the immune response, they are not directly involved in the production of autoantibodies against desmoglein proteins. Plasma cells are specifically responsible for this function.

C. Neutrophils: Neutrophils are part of the innate immune response and are primarily involved in phagocytosis and bacterial defense. They are not directly involved in the pathogenesis of pemphigus and do not produce autoantibodies against desmoglein proteins.

**Clinical Pearl:**
The understanding of the involvement of plasma cells in pemphigus is crucial for understanding the pathogenesis of this autoimmune disease. This knowledge enables physicians to diagnose, treat, and manage pemphigus patients effectively, as well as differentiate it from other skin diseases with similar clinical presentations.