Numerous HIV-specific lymphocyte clones have been isolated from HIV-infected per

ID: 63004 • Letter: N

Question

Numerous HIV-specific lymphocyte clones have been isolated from HIV-infected persons. One of these clones, UrSTD2, produced cytokines when stimulated with a synthetic, European HIV strain-derived peptide (HIV-DP1, whose amino acid sequence was LQVINGKES), using autologous dendritic cells (DCs) as antigen-presenting cells. However, allogeneic DCs loaded with HIV-DP1 failed to stimulate the UrSTD2 clone and no cytokines were produced. Autologous DCs loaded with a corresponding HIV peptide from a different European HIV strain (HIV-DP2, whose amino acid sequence was LQPINGYES) also stimulated UrSTD2 lymphocytes. In contrast, the same autologous DCs loaded with HIV-DP3 (LQVINGYEF) or HIV-DP4 (LQPINGKEM) [corresponding peptides from 2 African strains of HIV] did not stimulate UrSTD2 lymphocytes. The same results were obtained in repeated experiments. From these results, one can conclude that [complete the sentence and (based on your immunology knowledge) assess the resulting statements (1-47) as either factually correct (= “true”) or incorrect (= “false”)]:

Explanation / Answer

Here autologous dendritic cells (obtained from the same individual) loaded with European HIV derived peptide (HIV-DP1) is capable stimulating UrSTD2 clone and thus making it to produce cytokines as the clone has been produced specific for the European HIV strain. But when the same autologous dendritic cells were loaded with Peptides HIV-DP3 and HIV-DP4 from an African strain, it did not stimulate the UrSTD2 clone as the two peptides HIV-DP3 having different amino acid at 7 and 9 and DP4 are at 3 and 9. Because of this, the T cell Receptor is not able to recognize these peptides with different amino acids, so it is not getting activated to produce the cytokines.

Peptide

Amino acid sequence

HIV-DP1

LQVINGKES

HIV–DP3

LQVINGYEF

HIV-DP4

LQPINGKEM