T-cell antigen receptors are distinguished from antibodies by which of the following

Correct Answer: B

Rationale: The correct answer is B. T-cell receptors must interact with antigens uniquely presented by other cells but not with free antigen. This is because T-cell receptors recognize antigens that are processed and presented on the surface of other cells via major histocompatibility complex (MHC) molecules. T-cell receptors specifically bind to the antigen-MHC complex, allowing T-cells to respond to specific foreign antigens. A: T-cell receptors are not distinguished from antibodies by glycosylation. Both T-cell receptors and antibodies can be glycosylated, so this does not differentiate them. C: T-cell receptors do not bind various cytokines. Cytokine receptors are separate entities that mediate cellular responses to cytokines. D: T-cell receptors do not bind complement to lyse cells. Complement activation is a separate immune response mechanism not involving T-cell receptors.

Correct Answer: B

Rationale: The correct answer is B: Bursitis. The employee's complaint of shoulder pain on abduction, localized pain with a specific trigger (racquetball tournament), and no mention of trauma or instability suggest an inflammatory condition like bursitis. The other choices are incorrect because a rotator cuff tear typically presents with weakness, dislocation with a history of trauma and visible deformity, and subluxation with recurrent episodes of partial dislocation.

Correct Answer: D

Rationale: Step 1: The patient complains of shortness of breath and has audible wheezes, indicating potential respiratory distress. Step 2: Oxygen saturation of 76% is critically low and requires immediate intervention. Step 3: Raising the patient to a high Fowler position helps improve lung expansion and oxygenation. Step 4: This action takes priority to improve the patient's breathing and oxygen saturation levels. Summary: A is incorrect as establishing an IV line is not the immediate priority. B is incorrect as informing the charge nurse delays direct patient care. C is incorrect as addressing the family is secondary to addressing the patient's urgent needs.

Correct Answer: B

Rationale: The correct answer is B: The shape of antigens. T cells recognize antigens based on their shape, specifically the conformational structure of the antigen. T cell receptors interact with the surface of antigens, forming a complex based on the shape complementarity. This interaction is crucial for T cell activation and immune response. A: Linear peptides - While T cells can recognize linear peptides presented by MHC molecules, the primary mode of recognition is through the shape of antigens. C: Buried epitopes - T cells typically recognize epitopes displayed on the surface of antigens rather than buried within the structure. D: Soluble antigens - T cells can recognize both soluble and membrane-bound antigens, but the key factor is the shape rather than the solubility of the antigen.

Correct Answer: C

Rationale: The correct answer is C: Paracortex. Naïve T cells circulate through the blood and lymphatic system until they encounter antigens presented by activated dendritic cells in the paracortex of lymph nodes. The paracortex is the region where T cell activation and proliferation occur, leading to an immune response. The subcapsular sinus (A) is primarily involved in filtering lymph fluid, the cortex (B) contains B cell follicles, and the medulla (D) contains plasma cells and macrophages. Thus, the paracortex is the specific site of interaction between naïve T cells and activated dendritic cells in lymph nodes.