CD26 expression in donor stem cell harvest and its correlation with engraftment in human haematopoietic stem cell transplantation: potential predictor of early engraftment.

BACKGROUND: The efficiency of haematopoietic stem and progenitor cells (HSPCs) is important when donor cell numbers are limiting. Stable white blood cell (WBC) and platelet engraftment is crucial for the outcome of haematopoietic stem cell transplantation (HSCT). DESIGN: This article evaluates CD26/dipeptidyl peptidase-IV expression on mobilised peripheral blood stem cell (PBSC) harvest of donors and its correlation with engraftment in HSCT. We have analysed CD26 expression on cells in various gates, that is, lymphocytes, monocytes, neutrophils and all populations using flow cytometry tool. RESULTS: Ours is the first study on human mobilised PBSC harvest from cancer patients or allogeneic related donors (n = 28) to demonstrate that increased CD26 expression leads to early engraftment in transplanted cancer patients. Correlation of CD26 expression with WBC engraftment was statistically significant (lymphocyte gate: P < 0.00001; monocyte gate: P < 0.00001; neutrophil gate: P < 0.00001; all populations: P < 0.00001). CD34 expression is a known predictor of engraftment. Nevertheless, there was no correlation between CD34 and CD26 expression in these cases. CONCLUSIONS: This study has given important leads indicating that CD26 expression may be an independent predictor of engraftment. Further study with large number of patients as well as study on circulatory CD26 may add valuable information towards improving current knowledge on CD26.

Ability of lymphokine-activated killer cells to lyse mycobacteria-infected cells.

Lymphokine-activated killer (LAK) cells were generated by interleukin-2 activation of peripheral blood lymphocytes obtained from lepromatous leprosy (LL) patients and healthy individuals. The ability of LAK cells to lyse targets (macrophages and T-24, a bladder carcinoma cell line) infected with mycobacteria (Mycobacterium leprae and mycobacterial strain ICRC) was assessed in a 51 chromium-release assay. It was observed that LAK cells generated from LL patients and healthy individuals could preferentially lyse M. leprae or ICRC-pulsed macrophages and T-24 cells, compared to non-pulsed targets. The ability of LAK cells to kill intracellular mycobacteria was demonstrated in colony forming assays. These results indicate a promising role for LAK cells in immunotherapy of leprosy.

Immunoprecipitation of mycobacterial antigens with sera from patients with leprosy.

Pooled sera from leprosy patients across the clinical spectrum, tuberculosis patients and healthy individuals were tested for their reactivity with antigens of Mycobacterium leprae and a panel of cultivable mycobacteria by immunoprecipitation technique. Sera from lepromatous leprosy patients demonstrated exclusive reactivity with the 26-kDa protein of M. tuberculosis H37Ra, 28-kDa protein of M. kansasii, 45-kDa protein of M. smegmatis, and 158, 40 and 14 kDa proteins of M. phlei. Sera from patients with borderline tuberculoid leprosy, tuberculoid leprosy, tuberculosis and health individuals failed to identify these antigens. Our studies indicate that analysis and characterization of immunodominant antigenic epitopes present on proteins of cultivable mycobacteria, sharing cross-reactive epitopes with M. leprae may prove to be important in the serodiagnosis of multibacillary leprosy as well as for developing vaccines for immunotherapy of leprosy.