**Core Concept**
The question is testing the understanding of lymph node histology and immunology, specifically the distribution and function of different lymphocyte subsets in the lymph node. The paracortical areas of the lymph node are primarily populated by **T lymphocytes**.

**Why the Correct Answer is Right**
Given the decrease in lymphocytes in the paracortical areas, which are rich in **T cells**, one would expect a relative increase or normal numbers of other cell types in the peripheral blood to compensate or reflect the underlying pathology. Since **B cells** are primarily found in the follicles and not in the paracortical areas, a decrease in T cells could result in a relative increase or normal numbers of **B cells** (CD19 or CD20 positive) in the blood.

**Why Each Wrong Option is Incorrect**
**Option A:** This would be incorrect because a decrease in paracortical lymphocytes suggests a problem with T cell areas, not an increase in T cells.
**Option C and D:** Without specific details on these options, the general principle is that a decrease in one lymphocyte subset (like T cells in the paracortical area) might lead to a relative increase or normal appearance of other subsets in the blood, but specific effects depend on the subset in question.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the paracortical areas of lymph nodes are crucial for cell-mediated immunity, primarily involving **T cells**. Any disruption here can lead to significant immunological consequences.

**Correct Answer:** Correct Answer: B. CD19 or CD20 (B cells).