## **Core Concept**
The question tests knowledge of immunoglobulin production, specifically focusing on IgE, which is a type of antibody involved in allergic reactions and parasitic infections. Immunoglobulins, or antibodies, are produced by B cells (B lymphocytes) as part of the adaptive immune response.

## **Why the Correct Answer is Right**
IgE is secreted by **plasma cells**, which are mature B cells that have been activated to produce large amounts of specific antibodies. Upon activation, B cells differentiate into plasma cells, which are the effector cells responsible for antibody production. IgE antibodies play a crucial role in triggering allergic reactions by binding to allergens, which then leads to the release of histamine and other mediators from mast cells.

## **Why Each Wrong Option is Incorrect**
- **Option A:** T cells (T lymphocytes) are involved in cell-mediated immunity and do not secrete immunoglobulins. They play a role in activating B cells but do not produce antibodies themselves.
- **Option B:** Mast cells are involved in the effector phase of allergic reactions and are not producers of IgE. They have IgE receptors on their surface and degranulate when IgE bound to their surface binds to an allergen.
- **Option C:** This option is not provided, but based on the context, we can infer that the correct answer is related to plasma cells.
- **Option D:** Neutrophils are a type of white blood cell involved in the innate immune response, particularly in phagocytosis, and are not producers of immunoglobulins.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that IgE levels can be elevated in allergic conditions and parasitic infections, making it a useful marker in the diagnosis and management of such diseases. Additionally, IgE is involved in type I hypersensitivity reactions, which include anaphylaxis, asthma, and atopic dermatitis.

## **Correct Answer:** B. Plasma cells.