Cell type which lacks HLA antigen is:
**Core Concept**
The HLA (Human Leukocyte Antigen) system is a group of genes that play a critical role in the immune system by encoding proteins responsible for the regulation of the immune response. These proteins are expressed on the surface of various immune cells, including T cells, B cells, and antigen-presenting cells, and are essential for the recognition and presentation of antigens to T cells.
**Why the Correct Answer is Right**
Red blood cells (RBCs) lack HLA antigens on their surface. This is because RBCs do not express the major histocompatibility complex (MHC) class I molecules, which are the cellular components responsible for presenting antigens to T cells. The absence of HLA antigens on RBCs makes them less immunogenic and reduces the risk of graft-versus-host disease in transfusion medicine.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not mentioned in the question, so we cannot evaluate it. However, we can discuss the other options.
**Option B:** This option is incorrect because platelets do express HLA antigens on their surface, which can lead to platelet activation and aggregation in the presence of antibodies.
**Option C:** This option is incorrect because plasma cells, which are a type of B cell, express HLA class I and II molecules on their surface.
**Clinical Pearl / High-Yield Fact**
When transfusing blood products, it is essential to match the HLA antigens of the donor and recipient to minimize the risk of an adverse immune response. Red blood cells, which lack HLA antigens, can be transfused without matching, but other blood products, such as platelets and plasma, require HLA matching.
**Correct Answer: D. Red blood cells.**