Vasopressin acts on blood vessels leading to their constriction. Which one of the following signaling cascades will apply to the effect of vasopressin?

• V₁R → Phosphatidylinositol hydrolysis → Ca²⁺ increase

• V₁R → Adenylate cyclase → cAMP

• V₂R → Phosphatidylinositol hydrolysis → Ca²⁺ increase

• V₂R → Adenylate cyclase → cAMP

Among the following antigens specific to a pathogen, which one is likely to be ineligible as a vaccine with long-lasting host protective effect?

• A cell surface protein

• An enzyme involved in pathogen metabolism.

• A signaling intermediate, which is a kinase.

• A long chain fatty acid

Cyclins are the regulatory subunits and cyclin-dependent kinases (CDKs) are the catalytic subunits. Following diagram represents the involvement of cyclins and CDKs in various stages of the cell cycle:

If we knock down cyclin D in a cell by shRNA, which one of the following graphs correctly represents the level of CDK2 activity?

In a plaque-forming cell assay, antigen specific B-cell numbers are assessed. In this assay, antigen coated sheep red blood cells (SRBCs) are lysed by the hapten-specific B-cells by complement-mediated cytotoxicity. In an assay that tried to enumerate the TNP-specific B-cells elicited in TNP-KLH-primed mice, no plaques were formed despite the presence of antigen-specific anybody producing B cells. Which of the following is NOT the reason for the absence of plaques?

• The source of complement has anti-TNP antibody.

• The SRBC were stored for too long.

• The B cells were contaminated with LPS or lectins.

• The complement had an anti-KLH antibody.

The following statements have been proposed for a cancer cell.

A. Binding of p53 with MDM2, a ubiquitin E3 ligase, is a precondition for cancer progression.

B. Phosphorylation of a tyrosine residue in the C-terminus of human c-Src is essential for cell invasion and motility.

C. Loss of function of both alleles of a tumor suppressor gene prevents metastasis.

D. Dimerization of c-myc-Max leads to enhanced cell proliferation.

Which of the combinations of the above statements is correct?

• A and B

• C and D

• A and D

• B and C

CD4⁺T cells are co-cultured with macrophages in the presence of immobilized anti-CD3 antibody under four different conditions:

(A) Interleukin (IL)-4 plus anti-IFNγ antibody.

(B) IL-12 and anti-IL-4 antibody.

(C) transforming growth factor (TGF)-β,

(D) TGF-β and IL-6

for three rounds to induce T-helper cell differentiation identifiable by the cytokines they express predominantly.

Which one of the following is the most likely combination of predominant cytokine expression in these cultures?

• (A) IL-4; (B) IFN-γ; (C) IL-10; (D) IL-17

• (A) IFN-γ; (B) IL-4; (C) IL-17; (D) IL-10

• (A) IL-17; (B) IL-4; (C) IFN-γ; (D) IL-10

• (A) IL-17; (B) IL-10; (C) IL-4; (D) IFN-γ

Activation of the Wnt signal transduction pathway is extremely important during early development. Of the various pathways, which one of the following is most likely to induce cytoskeletal changes, like cell shape and movement?

A technician wanted to make rabbit antiserum specific for mouse IgG. The technician injected rabbit with purified mouse IgG but obtained antiserum which reacted strongly with each of the other mouse isotopes. Which of the procedures mentioned below will allow him to make antiserum specific for IgG only?

• Injecting rabbit with purified F(ab)₂' region of the IgG antibody.

• Injecting rabbit with purified heavy chain of the IgG antibody.

• Injecting rabbit with purified light chain of the IgG antibody.

• Injecting rabbit with purified F(ab)' region of the IgG antibody.

Which one of the following statements about cell-cell interactions is NOT true?

A. Cadherins are transmembrane linker proteins which carry out Ca²⁺-mediated adhesion between adjacent cells.

B. Integrins are transmembrane adhesion proteins that mediate homophilic adhesion through actin and intermediate filaments.

C. Selectins are cell surface lectins that mediate a variety of transient, cell-cell adhesion interactions in the bloodstream.

D. ICAMs (intracellular cell adhesion molecules) and VCAMs (vascular cell adhesion molecules) are members of immunoglobulin (Ig) superfamily.

• Only A

• Only B

• Both C and D

• Both A and D

In an experiment to detect a new protein in fixed cells, no secondary antibody tagged with fluorescence dye is available. What should be the best choice out of the following to detect the protein?

• Protein A-FITC

• Protein A-Sepharose

• Biotin-FITC

• Avidin-FITC