Purpose: Predicting late effects in patients treated with radiation therapy by assessing in vitro radiation-induced CD4 and CD8 T-lymphocyte apoptosis can be useful in individualizing treatment. Experimental Design: In a prospective study, 399 curatively irradiated patients were tested using a rapid assay where fresh blood samples were in vitro irradiated with 8 Gy X-rays. Lymphocytes were collected and prepared for flow cytometric analysis. Apoptosis was assessed by associated condensation of DNA. The incidences of late toxicities were compared for CD4 and CD8 T-lymphocyte apoptoses using receiver-operating characteristic curves and cumulative incidence. Results: No association was found between early toxicity and T-lymphocyte apoptosis. Grade 2 and 3 late toxicities were observed in 31% and 7% of patients, respectively. More radiationinducedT-lymphocyte apoptosis was significantly associated with less grade 2 and 3 late toxicity (Gray's test, P < 0.0001). CD8 (area under the curve = 0.83) was more sensitive and specific than CD4. No grade 3 late toxicity was observed for patients with CD4 and CD8 values greater than 15% and 24%, respectively. The 2-year cumulative incidence for grade 2 or 3 late toxicity was 70%, 32%, and 12% for patients with absolute change in CD8 T-lymphocyte apoptosis of V16, 16 to 24, and >24, respectively.Conclusions: Radiation-induced T-lymphocyte apoptosis can significantly predict differences in late toxicity between individuals. It could be used as a rapid screen for hypersensitive patients to radiotherapy. In future dose escalation studies, patients could be selected using the apoptosis assay.

Patients after polytrauma, burns, or septic shock frequently develop a life-threatening immunodeficiency. This state is associated with specific functional alterations of monocytic cells. We previously proposed endotoxin tolerance, the monocyte state after acute response to lipopolysaccharide, as a respective model system. One major feature in both the clinical situation and the in vitro model is the dramatic down-regulation of monocyte major histocompatibility complex (MHC) class II surface expression, which is associated with impaired antigen presentation capacity. This study focused on the mechanisms behind reduced MHC class II expression in endotoxin tolerance. Endotoxin priming provoked a decrease of monocyte intracellular MHC class II. It also led to a reduced expression of the chaperonic invariant chain and to an inhibited synthesis of the major lysosomal enzyme for final cleavage of the invariant chain going along with a relative accumulation of p10. The expression of HLA-DM necessary for loading MHC class II with antigenic peptide was also decreased. Additionally, reduced export of MHC class II ␣␤ complexes to the cell surface was observed. The down-regulation of HLA-DR, invariant chain, and HLA-DM was regulated at the mRNA level and may be the consequence of reduced class II transactivator expression observed in this study. The simultaneous interference at different regulatory levels may explain the uniquely strong and long lasting MHC class II down-modulating effect of endotoxin priming compared with transforming growth factor-␤ and interleukin-10. These results not only contribute to a better understanding of experimental endotoxin tolerance but may also give rise to new therapeutics for temporary immunodeficiency and, conversely, for MHC class II-dependent diseases such as autoimmunity and transplant rejection.The exposition of monocytes toward already minor amounts of endotoxin (LPS) 1 provokes a massive inflammatory response of these cells. However, after initial LPS response, these cells show a modified reaction toward repeated LPS exposure. Such monocytes produce only minor amounts of proinflammatory cytokines, including TNF-␣, IL-1␤, and IL-12, as well as NO, whereas the production of IL-1 receptor antagonist and TNF receptor II was not altered or actually increased (1-6). This monocytic state after initial LPS priming is therefore designated as endotoxin tolerance. We previously showed that this altered capacity to respond to LPS was paralleled by a strong and long lasting down-regulation of MHC class II expression on these monocytes occurring after a transient up-regulation of this molecule during LPS priming. The reduced MHC class II expression was associated with diminished monocyte T-cell stimulation capacity (7). Very similar alterations of monocyte function as shown in experimental endotoxin tolerance are also observed in patients after surgery, polytrauma, and septic shock. These patients frequently develop a temporary immunodeficiency, which in its most severe form is referred to as im...

Purpose: Evidence has accumulated in recent years suggestive of a genetic basis for a susceptibility to the development of radiation injury after cancer radiotherapy. The purpose of this study was to assess whether patients with severe radiation-induced sequelae (RIS; i.e., National Cancer Institute/CTCv3.0 grade, z3) display both a low capacity of radiation-induced CD8 lymphocyte apoptosis (RILA) in vitro and possess certain single nucleotide polymorphisms (SNP) located in candidate genes associated with the response of cells to radiation. Experimental Design: DNA was isolated from blood samples obtained from patients (n = 399) included in the Swiss prospective study evaluating the predictive effect of in vitro RILA and RIS. SNPs in the ATM, SOD2, XRCC1, XRCC3, TGFB1, and RAD21 genes were screened in patients who experienced severe RIS (group A, n = 16) and control subjects who did not manifest any evidence of RIS (group B, n = 18). Results: Overall, 13 and 21 patients were found to possess a total of <4 and z4 SNPs in the candidate genes. The median (range) RILA in group A was 9.4% (5.3-16.5) and 94% (95% confidence interval, 70-100) of the patients (15 of 16) had z4 SNPs. In group B, median (range) RILA was 25.7% (20.2-43.2) and 33% (95% confidence interval, 13-59) of patients (6 of 18) had z4 SNPs (P < 0.001). Conclusions:The results of this study suggest that patients with severe RIS possess 4 or more SNPs in candidate genes and low radiation-induced CD8 lymphocyte apoptosis in vitro.

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