Question

_______ must compete with each other to gain access to antigen on a FDC.

a. Centrocytes
b. Centroblasts
c. TFH cells
d. A & B
e. A, B & C

Answer 1

Centrocytes and centroblasts must compete to access antigens on FDCs. T cells bind differently to MHC molecules, with Helper T cells using MHC II and CTLs using MHC I. All nucleated cells present MHC I molecules, aiding in recognition and immune response.

Step-by-step explanation:

The cells that must compete with each other to gain access to antigen on a Follicular Dendritic Cell (FDC) are both centrocytes and centroblasts. This is because these B cells are located in the germinal center of a lymph node and are involved in the affinity maturation and clonal selection processes during an immune response. The correct answer to the question is therefore "A & B".

When discussing antigen presentation and T cells, it's important to note that CD4+ Helper T cells bind to MHC II molecules on Antigen-Presenting Cells (APCs), whereas CD8+ Cytotoxic T Cells (CTLs) bind to MHC I molecules. MHC I molecules are found on all nucleated cells, and the primary role of CTLs is to kill infected or damaged cells. Helper T cells release cytokines to assist other immune cells, while CTLs directly attack cells presenting antigens with MHC I molecules.

On the topic of antigen-presentation by B cells and T cells, MHC II molecules are also involved as they help distinguish cells as self and aid in the immune response. CD4+ T cell precursors are indeed formed in the bone marrow and then migrate to the thymus, where they develop their T cell receptors. Lastly, when a CD4+ helper T cell binds an MHC II-antigen complex on an antigen-presenting cell, both the T cell and the APC release cytokines to propagate the immune response.

Answer 2

Centrocytes and centroblasts must compete for antigen on FDCs, hence the answer is d. A & B. TCRs of CD4+ helper T cells bind to antigens presented with MHC II, while CD8+ cytotoxic T cells bind to antigens presented with MHC I on APCs.

Step-by-step explanation:

The immune cells that must compete with each other to gain access to antigen on a Follicular Dendritic Cell (FDC) are both centrocytes and centroblasts. However, TFH cells, also known as T Follicular Helper cells, do not compete for antigen on FDCs in the same way.

To address some background knowledge, CD8+ T cells, also known as cytotoxic T lymphocytes (CTLs), bind to MHC I molecules on Antigen-Presenting Cells (APCs) via their CD8 coreceptors. MHC I molecules are found on virtually all nucleated cells, enabling these cells to present endogenous antigens to cytotoxic T cells. On the other hand, MHC II molecules are present on professional APCs such as dendritic cells, macrophages, and B cells, and are used for presenting exogenous antigens to CD4+ helper T cells.

Regarding T cell properties, it is false that MHC II is found on most body cells, as it is primarily on professional APCs. T cell receptors (TCRs) are found on both CD4+ and CD8+ T cells, which bind to MHC II and MHC I respectively. While helper T cells (CD4+) release cytokines and assist other immune cells, cytotoxic T cells (CD8+) directly kill infected or cancerous cells.