Proteogenomic-based discovery of minor histocompatibility antigens with suitable features for immunotherapy of hematologic cancers.

Pre-clinical studies have shown that injection of allogeneic T cells primed against a single minor histocompatibility antigen (MiHA) could cure hematologic cancers (HC) without causing any toxicity to the host. However, translation of this approach in humans has been hampered by the paucity of molecularly defined human MiHAs. Using a novel proteogenomic approach, we have analyzed cells from 13 volunteers and discovered a vast repertoire of MiHAs presented by the most common HLA haplotype in European Americans: HLA-A*02:01;B*44:03. Notably, out of >6000 MiHAs, we have identified a set of 39 MiHAs that share optimal features for immunotherapy of HCs. These 'optimal MiHAs' are coded by common alleles of genes that are preferentially expressed in hematopoietic cells. Bioinformatic modeling based on MiHA allelic frequencies showed that the 39 optimal MiHAs would enable MiHA-targeted immunotherapy of practically all HLA-A*02:01;B*44:03 patients. Further extension of this strategy to a few additional HLA haplotypes would allow treatment of almost all patients.

The perlecan fragment LG3 regulates homing of mesenchymal stem cells and neointima formation during vascular rejection.

Transplant vasculopathy is associated with neointimal accumulation of recipient-derived mesenchymal stem cells. Increased circulating levels of LG3, a C-terminal fragment of perlecan, were found in renal transplant patients with vascular rejection. Here, we evaluated whether LG3 regulates the migration and homing of mesenchymal stem cells and the accumulation of recipient-derived neointimal cells. Mice were transplanted with a fully-MHC mismatched aortic graft followed by intravenous injection of recombinant LG3. LG3 injections increased neointimal accumulation of α-smooth muscle actin positive cells. When green fluorescent protein (GFP)-transgenic mice were used as recipients, LG3 injection favored accumulation of GFP+ cells to sites of neointima formation. LG3 increased horizontal migration and transmigration of mouse and human MSC in vitro and led to increased ERK1/2 phosphorylation. Neutralizing ß1 integrin antibodies or use of mesenchymal stem cells from α2 integrin-/- mice decreased migration in response to recombinant LG3. Reduced intima-media ratios and decreased numbers of neointimal cells showing ERK1/2 phosphorylation were found in α2-/- recipients injected with recombinant LG3. Collectively, our results suggest that LG3, through interactions with α2ß1 integrins on recipient-derived cells leading to activation of ERK1/2 and increased migration, favors myointimal thickening.

Disturbance in uniformly 13C-labelled DHA metabolism in elderly human subjects carrying the apoE ε4 allele.

Carrying the apoE ε4 allele (E4+ ) is the most important genetic risk for Alzheimer's disease. Unlike non-carriers (E4- ), E4+ seem not to be protected against Alzheimer's disease when consuming fish. We hypothesised that this may be linked to a disturbance in n-3 DHA metabolism in E4+. The aim of the present study was to evaluate [13C]DHA metabolism over 28 d in E4+ v. E4-. A total of forty participants (twenty-six women and fourteen men) received a single oral dose of 40 mg [13C]DHA, and its metabolism was monitored in blood and breath over 28 d. Of the participants, six were E4+ and thirty-four were E4-. In E4+, mean plasma [13C]DHA was 31% lower than that in E4-, and cumulative b-oxidation of [13C]DHA was higher than that in E4- 1­28 d post-dose (P ≤0·05). A genotype x time interaction was detected for cumulative b-oxidation of [13C]DHA (P ≤ 0·01). The whole-body half-life of [13C]DHA was 77% lower in E4+ compared with E4- (P ≤0·01). In E4+ and E4-, the percentage dose of [13C]DHA recovered/h as 13CO2 correlated with [13C]DHA concentration in plasma, but the slope of linear regression was 117% steeper in E4+ compared with E4- (P ≤ 0·05). These results indicate that DHA metabolism is disturbed in E4+, and may help explain why there is no association between DHA levels in plasma and cognition in E4+. However, whether E4+ disturbs the metabolism of 13C-labelled fatty acids other than DHA cannot be deduced from the present study.

The TGF-ß-Smad3 pathway inhibits CD28-dependent cell growth and proliferation of CD4 T cells.

Transforming growth factor-ß (TGF-ß) maintains self-tolerance through a constitutive inhibitory effect on T-cell reactivity. In most physiological situations, the tolerogenic effects of TGF-ß depend on the canonical signaling molecule Smad3. To characterize how TGF-ß/Smad3 signaling contributes to maintenance of T-cell tolerance, we characterized the transcriptional landscape downstream of TGF-ß/Smad3 signaling in resting or activated CD4 T cells. We report that in the presence of TGF-ß, Smad3 modulates the expression of >400 transcripts. Notably, we identified 40 transcripts whose expression showed Smad3 dependence in both resting and activated cells. This 'signature' confirmed the non-redundant role of Smad3 in TGF-ß biology and identified both known and putative immunoregulatory genes. Moreover, we provide genomic and functional evidence that the TGF-ß/Smad3 pathway regulates T-cell activation and metabolism. In particular, we show that TGF-ß/Smad3 signaling dampens the effect of CD28 stimulation on T-cell growth and proliferation. The impact of TGF-ß/Smad3 signals on T-cell activation was similar to that of the mTOR inhibitor Rapamycin. Considering the importance of co-stimulation on the outcome of T-cell activation, we propose that TGF-ß-Smad3 signaling may maintain T-cell tolerance by suppressing co-stimulation-dependent mobilization of anabolic pathways.

Differential expression of SMAD3 transcripts is not regulated by cis-acting genetic elements but has a gender specificity.

As a key component of the transforming growth factor-beta (TGF-beta) pathway, SMAD3 plays an essential role in development and maintenance of self-tolerance. Furthermore, a recent study based on gene-expression profiling in donors of allogeneic hematopoietic cell grafts revealed that the level of expression of several components of the TGF-beta pathway can predict the occurrence of graft-versus-host disease (GVHD) in recipients. The gene with the best GVHD predictive accuracy was SMAD3: no recipients suffered from GVHD when their donor cells expressed high levels of SMAD3 transcripts. The present study had two specific aims: to validate differential expression of SMAD3 transcripts in an independent and larger cohort of subjects and to determine whether interindividual differences were dictated by cis-acting genetic elements. In a cohort of 397 subjects, we found that SMAD3 transcript levels varied over a sixfold range. Analyses of SMAD3 single nucleotide polymorphisms and of SMAD3 promoter methylation patterns provide compelling evidence that interindividual differences in SMAD3 transcript levels do not result from in-cis genetic variations. Of note, part of the variance in SMAD3 expression was gender related as women expressed lower levels of SMAD3 transcripts than men.

Adoptive transfer of minor histocompatibility antigen-specific T lymphocytes eradicates leukemia cells without causing graft-versus-host disease.

Adoptive transfer of T cells reactive to minor histocompatibility antigens has the unmatched ability to eradicate malignant hematopoietic cells. Unfortunately, its use is hampered by the associated graft-versus-host disease. The critical issue of a possible dissociation of the antileukemic effect and graft-versus-host disease by targeting specific minor histocompatibility antigens remains unresolved because of the unknown nature and number of minor histocompatibility antigens necessary or sufficient to elicit anti-leukemic activity and graft-versus-host disease. We found that injection of T lymphocytes primed against a single major histocompatibility complex class I-restricted immunodominant minor histocompatibility antigen (B6dom1) caused no graft-versus-host disease but produced a curative anti-leukemic response. Avoidance of graft-versus-host disease required that no other host-reactive T cells be co-injected with T cells primed with B6dom1. Here we show that effective and non-toxic immunotherapy of hematologic malignancies can be achieved by targeting a single immunodominant minor histocompatibility antigen.

Immunodomination results from functional differences between competing CTL.

The presence of dominant epitopes suppresses generation of CTL activity toward other non-dominant epitopes found on the same antigen-presenting cell (APC). This phenomenon, termed immunodomination, drastically restricts the diversity of the repertoire of CTL responses. Under various experimental conditions we assessed the in vivo expansion by tetramer staining and function by expression of O-glycans and intracellular perforin of CTL specific for a dominant (B6(dom1)) and a non-dominant (HY) H2D(b)-restricted epitope. Immunodomination abrogated expansion rather than differentiation of HY-specific CTL. When immunodomination was precluded because HY was presented alone or because high numbers of antigen-bearing APC were present, the numbers of HY-specific T cells detected after antigen priming were similar to those of B6(dom1)-specific T cells. The main difference between T cells that recognized B6(dom1) versus HY was functional rather than quantitative. The key feature of T cells specific for B6(dom1) is that they show striking up-regulation of molecules involved in CTL effector activity rather than accumulating to particularly high levels, as assessed by tetramer staining. These results support the emerging concept that following antigen priming, CTL populations of similar size can display important differences in effector function, and suggest that these functional differences are instrumental in shaping the repertoire of CTL responses.

Allogeneic transplantation for multiple myeloma: further evidence for a GVHD-associated graft-versus-myeloma effect.

We report a series of 37 consecutive patients with multiple myeloma (MM) who received an allograft between 1990 and 2000 at our institution. Median age was 47 years, and nearly 70% of patients were Durie-Salmon stage III. A median of five cycles of chemotherapy were given before transplant, with a median interval between diagnosis and transplant of 9.3 months. We report a nonrelapse mortality rate of 22% with a median follow-up period of 40 months, whereas complete remission (CR) rate at 12 months is estimated at 57%. Treatment failure rate and overall survival at 40 months are estimated at 52% and 32%, respectively. The number of chemotherapy cycles prior to allotransplantation achieved borderline statistical significance as a poor prognosis factor for overall survival (P = 0.05), while the presence of chronic graft-versus-host disease (cGVHD) was significantly correlated with CR achievement (P = 0.036). Our study confirms that early allografting in MM can yield toxicity rates significantly lower than those associated with historical cohorts, and supports the hypothesis that cumulative chemotoxicity has a negative influence on mortality and survival rates. More importantly, our study clearly demonstrates an association between cGVHD and CR and brings further evidence in favor of a graft-versus-myeloma effect.

Immunobiology of allogeneic peripheral blood mononuclear cells mobilized with granulocyte-colony stimulating factor.

The use of mobilized peripheral blood (PB) stem cells for autologous transplantation initially generated much enthusiasm because of enhanced engraftment in comparison to marrow stem cells and avoidance of general anesthesia for the donor. Its application to the allogeneic setting seemed inevitable. For obvious ethical reasons, allogeneic donors are mobilized with cytokines only, mainly granulocyte colony-stimulating factor (G-CSF). Results from preliminary studies suggest that in comparison to standard bone marrow transplants, outcomes such as engraftment, host-versus-graft reaction, graft-versus-host disease, graft-versus-leukemia and immunological reconstitution may be different. Surprisingly, G-CSF, previously recognized as a late acting lineage-specific factor for neutrophil production, not only disrupts homeostasis between stem cells and their microenvironment, but also induces significant quantitative and qualitative changes in the accessory cell compartment, affecting lymphocytes, monocytes, natural killer, dendritic, and stromal cells. Furthermore, mobilization of huge numbers of non-professional antigen presenting cells (CD34+ stem cells) amplifies the tolerizing potential of PB stem cell grafts. Thus, G-CSF mobilization provides PB transplants with different immunobiologic properties in comparison to standard bone marrow grafts. Whether these immunobiologic differences will lead to better transplant outcomes remains to be shown through much awaited results of large randomized clinical trials.

Relapse after bone marrow transplantation: evidence for distinct immunological mechanisms between adult and paediatric populations.

Donor lymphocyte infusions are particularly effective for remission induction in malignant cells in patients who relapse after allogeneic progenitor cell transplantation (PCT) and who remain sensitive to the administration of unprimed donor T and/or natural killer (NK) cells present in donor lymphocyte infusions. To determine whether relapse after unmanipulated PCT could be ascribed to donor T and/or NK cell loss or tolerization, we evaluated the chimeric status of 81 patients with haematological malignancies who were receiving allogeneic unmanipulated PCT. The incidence of mixed chimaerism (MC) in unfractionated mononuclear leucocyte samples decreased rapidly after transplant, and was not detectable 4 months after PCT, even in patients who subsequently relapsed. The chimeric status of immune effector cell subsets was then evaluated in 15 patients at the time of relapse. All adults demonstrated complete donor haematopoiesis (CDH) for all cell lineages, whereas T- and NK-cell MC was only found in patients younger than age 13 years (P = 0.004). MC was not found in T nor NK cells of a control group consisting of age-matched paediatric patients in remission after allogeneic PCT. Thus, in adults, T and NK cell MC disappears early after unmanipulated allogeneic PCT and is absent at the time of relapse. However, the identification of donor T and NK cell loss in the paediatric relapsed but not remission patients suggests a distinct mechanism of relapse.

Regulation of extrathymic T cell development and turnover by oncostatin M.

Chronic exposure to oncostatin M (OM) has been shown to stimulate extrathymic T cell development. The present work shows that in OM transgenic mice, 1) massive extrathymic T cell development takes place exclusively the lymph nodes (LNs) and not in the bone marrow, liver, intestines, or spleen; and 2) LNs are the sole site where the size of the mature CD4+ and CD8+ T cell pool is increased (6- to 7-fold). Moreover, when injected into OM transgenic mice, both transgenic and nontransgenic CD4+ and CD8+ T cells preferentially migrated to the LNs rather than the spleen. Studies of athymic recipients of fetal liver grafts showed that lymphopoietic pathway modulated by OM was truly thymus independent, and that nontransgenic progenitors could generate extrathymic CD4+CD8+ cells as well as mature T cells under the paracrine influence of OM. The progeny of the thymic-independent differentiation pathway regulated by OM was polyclonal in terms of Vbeta usage, exhibited a phenotype associated with previous TCR ligation, and displayed a rapid turnover rate (5-bromo-2'-deoxyuridine pulse-chase assays). This work suggests that chronic exposure to OM 1) discloses a unique ability of LNs to sustain extrathymic T cell development, and 2) increases the number and/or function of LN niches able to support seeding of recirculating mature T cells. Regulation of the lymphopoietic pathway discovered in OM transgenic mice could be of therapeutic interest for individuals with thymic hypoplasia or deficient peripheral T cell niches.

The in vivo fate of APCs displaying minor H antigen and/or MHC differences is regulated by CTLs specific for immunodominant class I-associated epitopes.

The goal of this work was to evaluate the fate of APCs following interactions with T cells in unprimed mice with a normal T cell repertoire. We elaborated a model in which male adherent peritoneal mononuclear cells were injected into the foreleg footpads of naive female recipients mismatched for either minor or major histocompatibility Ags. At various times after injection, APC numbers in the draining (axillary and brachial) lymph nodes were assessed using a Ube1y gene-specific PCR assay. Our experimental model was designed so that the number of APCs expressing the priming epitope was similar to what is observed under real life conditions. Thus, early after injection, the frequency of afferent lymph-derived APCs expressing the priming epitope was in the range of 101-102/106 lymph node cells. We found that APCs presenting some, but not all, nonself epitopes were killed rapidly after entrance into the lymph nodes. Rapid elimination of APCs occurred following interactions with MHC class I-restricted, but not class II-restricted, T cells and was observed when APCs presented an immunodominant (B6dom1/H7a), but not a nondominant (HY), epitope. Killing of APCs was mediated partly, but not exclusively, by perforin-dependent process. We propose that killing of APCs by CTLs specific for immunodominant MHC class I-restricted epitopes may be instrumental in regulating the intensity, duration, and diversity of T cell responses.

Massive activation-induced cell death of alloreactive T cells with apoptosis of bystander postthymic T cells prevents immune reconstitution in mice with graft-versus-host disease.

After hematopoietic stem cell transplantation, the persistence and expansion of grafted mature postthymic T cells allow both transfer of donor immunologic memory and generation of a diverse T repertoire. This thymic-independent process, which is particularly important in humans, because most transplant recipients present severe thymus atrophy, is impaired by graft-versus-host disease (GVHD). The goal of this study was to decipher how GVHD influences the fate of grafted postthymic T cells. Two major findings emerged. First, we found that, after a brisk proliferation phase, alloreactive antihost T cells underwent a massive activation-induced cell death (AICD). For both CD4(+) and CD8(+) T cells, the Fas pathway was found to play a major role in this AICD: alloreactive T cells upregulated Fas and FasL, and AICD of antihost T cells was much decreased in the case of lpr (Fas-deficient) donors. Second, whereas non-host-reactive donor T cells neither upregulated Fas nor suffered apoptosis when transplanted alone, they showed increased membrane Fas expression and apoptosis when coinjected with host-reactive T cells. We conclude that GVHD-associated AICD of antihost T cells coupled with bystander lysis of grafted non-host-reactive T cells abrogate immune reconstitution by donor-derived postthymic T lymphocytes. Furthermore, we speculate that massive lymphoid apoptosis observed in the acute phase of GVHD might be responsible for the occurrence of autoimmunity in the chronic phase of GVHD.

Pathways in the offending process of extrafamilial sexual child molesters.

The aim of the current study was to investigate specific pathways in the offending process of extrafamilial sexual child molesters. Forty-four men who had committed at least one sexual offense against a nonfamilial prepubescent child were included in this study and were classified using cluster analysis. Subjects using the coercive pathway (n = 30) had generally used psychoactive substances before their offenses. Furthermore, they had molested a female victim without perceived vulnerability and whom they had already well known. These molesters had not planned their offense, which was of short duration (less than 15 min), and involved coital activities and coercion (verbal and/or physical). Subjects using the noncoercive pathway (n = 14) had generally used pornography and deviant sexual fantasies before their offenses. Moreover, they had molested a male victim, in whom they perceived a psychosocial vulnerability and who was not familiar to them. These molesters had planned their offense, which was of longer duration (more than 15 min) and involved noncoital activities without coercion. These two pathways were compared to the two pathways in the offending process identified by Ward and his colleagues.

Biochemical and immunogenetic analysis of an immunodominant peptide (B6dom1) encoded by the classical H7 minor histocompatibility locus.

Of the many minor histocompatibility (H) Ags that have been detected in mice, the ability to induce graft vs host disease (GVHD) after bone marrow transplantation is restricted to a limited number of immunodominant Ags. One such murine Ag, B6dom1, is presented by the H2-Db MHC class I molecule. We present biochemical evidence that the natural B6dom1 peptide is indistinguishable from AAPDNRETF, and we show that this peptide can be isolated from a wide array of tissues, with highest levels from the lymphoid organs and lung. Moreover, we employ a novel, somatic cell selection technique involving CTL-mediated immunoselection coupled with classical genetics, to show that B6dom1 is encoded by the H7 minor H locus originally discovered approximately 40 years ago. These studies provide a molecular genetic framework for understanding B6dom1, and exemplify the fact that mouse minor H loci that encode immunodominant CTL epitopes can correspond to classical H loci originally identified by their ability to confer strong resistance to tumor transplantation. Additionally, these studies demonstrate the utility of somatic cell selection approaches toward resolving H Ag immunogenetics.

The effect of graft-versus-host disease on T cell production and homeostasis.

The aim of this work was to decipher how graft-versus-host disease (GVHD) affects T cell production and homeostasis. In GVHD+ mice, thymic output was decreased fourfold relative to normal mice, but was sufficient to maintain a T cell repertoire with normal diversity in terms of Vbeta usage. Lymphoid hypoplasia in GVHD+ mice was caused mainly by a lessened expansion of the peripheral postthymic T cell compartment. In 5-bromo-2'-deoxyuridine pulse-chase experiments, resident T cells in the spleen of GVHD+ mice showed a normal turnover rate (proliferation and half-life). When transferred into thymectomized GVHD- secondary hosts, T cells from GVHD+ mice expanded normally. In contrast, normal T cells failed to expand when injected into GVHD+ mice. Thus, the reduced size of the postthymic compartment in GVHD+ mice was not due to an intrinsic lymphocyte defect, but to an extrinsic microenvironment abnormality. We suggest that this extrinsic anomaly is consistent with a reduced number of functional peripheral T cell niches. Therefore, our results show that GVHD-associated T cell hypoplasia is largely caused by a perturbed homeostasis of the peripheral compartment. Furthermore, they suggest that damage to the microenvironment of secondary lymphoid organs may represent an heretofore unrecognized cause of acquired T cell hypoplasia.

Seminal plasma choline phospholipid-binding proteins stimulate cellular cholesterol and phospholipid efflux.

Bovine seminal plasma (BSP) contains a family of phospholipid-binding proteins (BSP-A1/-A2, BSP-A3 and BSP-30-kDa, collectively called BSP proteins) that potentiate sperm capacitation induced by high-density lipoproteins. We showed recently that BSP proteins stimulate cholesterol efflux from epididymal spermatozoa and play a role in capacitation. Here, we investigated whether or not BSP proteins could stimulate cholesterol and phospholipid efflux from fibroblasts. Cells were radiolabeled ([3H]cholesterol or [3H]choline) and the appearance of radioactivity in the medium was determined in the presence of BSP proteins. Alcohol precipitates of bovine seminal plasma (designated crude BSP, cBSP), purified BSP-A1/-A2, BSP-A3 and BSP-30-kDa proteins stimulated cellular cholesterol and choline phospholipid efflux from fibroblasts. Efflux mechanistic differences were observed between BSP proteins and other cholesterol acceptors. Preincubation of BSP-A1/-A2 proteins with choline prevented cholesterol efflux, an effect not observed with apolipoprotein A-I. Also, the rate of BSP-induced efflux was rapid during the first 20 min, but leveled off thereafter in contrast to a relatively slow, but constant, rate of cholesterol efflux mediated by apolipoprotein A-I, apolipoprotein A-I-containing reconstituted lipoproteins (LpA-I) and high-density lipoproteins. These results indicate that fibroblasts are a good cell model to study the mechanism of lipid efflux mediated by BSP proteins.

Shaping the repertoire of cytotoxic T-lymphocyte responses: explanation for the immunodominance effect whereby cytotoxic T lymphocytes specific for immunodominant antigens prevent recognition of nondominant antigens.

The immunodominance effect, whereby the presence of immunodominant epitopes prevents recognition of nondominant determinants presented on the same antigen-presenting cell (APC) considerably restricts the repertoire of cytotoxic T lymphocyte (CTL) responses. To elucidate the molecular basis of the immunodominance effect, we compared the interactions of a dominant (B6(dom1)) and a nondominant epitope (H-Y) with their restricting class I molecule (H2-Db), and their ability to trigger cognate CTLs. We found that B6(dom1)/Db complexes behaved as optimal T-cell receptor (TCR) ligands and triggered a more rapid in vivo expansion of cognate CTLs than H-Y/Db complexes. The superiority of the dominant epitope was explained by its high cell surface density (1,012 copies/cell for B6(dom1) v 10 copies/cell for H-Y) and its optimal affinity for cognate TCRs. Based on these results, we conclude that dominant class I-associated epitopes are those that have optimal ability to trigger TCR signals in CTLs. We propose that the rapid expansion of CTLs specific for dominant antigens should enable them to compete more successfully than other CTLs for occupancy of the APC surface.

Development of a highly polymorphic STR marker for identity testing purposes at the human androgen receptor gene (HUMARA).

We developed a non-isotopic method which improves the technical quality of the X-linked HUMARA locus typing process. The use of formamide and a low concentration of acrylamide increased resolution and sharpness of HUMARA alleles in silver-stained polyacrylamide gels. In addition, the construction of an allelic ladder containing amplified sequence of 9 alleles (even-numbered alleles) of the HUMARA locus, allows confident, rapid and precise assignment of discretely defined alleles. Allele and genotype frequencies for the HUMARA locus were determined in a French Canadian population sample. Observed genotype frequencies in females conformed to Hardy-Weinberg expectations. Furthermore, the HUMARA locus is highly polymorphic with 18 observed alleles and an heterozygosity value of 89.3%. Also, this locus has average powers of discrimination of 97.8% and 88.7% for testing samples of female and male origin, respectively. In the French Canadian population, the average probability of excluding a random man as the father in paternity analysis when both mother and daughter are tested for this locus is 88.0%. Together, the results indicate that the HUMARA locus provides a highly discriminatory system that is appropriate for the purposes of forensic identification and paternity testing involving a female child.

Intraocular pressure change measured by Goldmann tonometry after laser in situ keratomileusis.

PURPOSE: To assess the accuracy of Goldmann tonometry after laser in situ keratomileusis (LASIK). SETTING: University-based refractive surgery group (Clinique du Laser Visuel). METHOD: The database of patients who had LASIK was retrospectively reviewed. Preoperative and postoperative intraocular pressure (IOP) was measured in 145 patients. The correlation between decrease in IOP and various preoperative and intraoperative parameters was evaluated by regression analysis. Only one eye in patients having bilateral surgery was used for statistical analysis. RESULTS: Laser in situ keratomileusis was associated with a mean decrease in IOP of 1.9 mm Hg +/- 2.9 (SD). There was no significant correlation between the decrease and any parameter evaluated. CONCLUSION: Intraocular pressure after LASIK decreased by a mean of 1.9 +/- 2.9 mm Hg. The cause of the decrease remains unknown.