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Clinical and Developmental Immunology
Volume 2013, Article ID 186420, 6 pages
Research Article

Ex Vivo Restimulation of Human PBMC Expands a T Cell Population That Can Confound the Evaluation of CD4 and CD8 T Cell Responses to Vaccination

1R&D Division, CSL Limited, Parkville, VIC 3052, Australia
2Influenza R&D Division, bioCSL Pty., Ltd., 63 Poplar Road, Parkville, VIC 3052, Australia

Received 30 April 2013; Revised 22 July 2013; Accepted 24 July 2013

Academic Editor: K. Blaser

Copyright © 2013 B. J. Sedgmen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The measurement of vaccine-induced humoral and and cellular immune responses represents an important correlate of vaccine efficacy. Accurate and reliable assays evaluating such responses are therefore critical during the clinical development phase of vaccines. T cells play a pivotal role both in coordinating the adaptive and innate immune responses and as effectors. During the assessment of cell-mediated immunity (CMI) in subjects participating in a large-scale influenza vaccine trial, we identified the expansion of an IFN- -producing T cell population in the peripheral blood of 90/610 (15%) healthy subjects. The appearance of T cells in the blood of subjects was transient and found to be independent of the study cohort, vaccine group, subject gender and ethnicity, and ex vivo restimulation conditions. Although the function of this population and relevance to vaccination are unclear, their inclusion in the total vaccine-specific T-cell response has the potential to confound data interpretation. It is thus recommended that when evaluating the induction of IFN- -producing and immune responses following vaccination, the T cells are either excluded or separately enumerated from the overall frequency determination.