PubMed Health⌕ Search

Biomedical subjects

C Keever

Publications and source records attributed to C Keever.

13 recordsLinked to original sources
PubMed1995

Analysis of reconstituting T cell receptor repertoires in bone marrow transplant recipients.

Allogeneic bone marrow transplantation (BMT) has become the treatment of choice for a variety of hematopoietic disorders. An important factor limiting the use of allogeneic BMT is delayed restoration of immune function. A quantitative understanding of immune reconstitution of the T cell compartment based on an efficient method of analysis would be of benefit. Distinct lineages of T cells which have resulted from previous and ongoing clonal expansion can be identified by their unique T cell receptors (TCR). Thus, TCR complexity can be used as a measure of repertoire complexity. Here we use a polymerase chain reaction-based approach which visualizes the size heterogeneity of the third complementarity determining region (CDR3) to study T cell reconstitution in adult bone marrow transplant recipients. We find that repertoire complexity, as determined by the number of bands of different length for each V family, reflects the general immune status of individuals tested. Contractions and gaps in repertoires are revealed in individuals suffering from recurrent infections associated with T cell impairment. This approach provides a new tool in the analysis of reconstitution of alpha/beta T cell repertoires and it can be also be applied to B cells and gamma/delta T cells.

Bone Marrow↗
PubMed1994

Circulating T cell repertoire complexity in normal individuals and bone marrow recipients analyzed by CDR3 size spectratyping. Correlation with immune status.

The analysis of the T cell repertoires involved in local or systemic immune responses is beginning to play an important role in many clinical situations. These include autoimmunity, response to viral or bacterial superantigens, alloimmunity including allograft rejection, and tumor immunity. Here we analyze circulating T cell repertoires by determining TCR beta-chain gene complexity using a modification of V beta family-specific PCR. This approach, called CDR3 size spectratyping, uses the size heterogeneity of the CDR3 as a further source of specificity in TCR analysis. It has been used here to analyze the complexity and stability of circulating T cell repertoires in normal adults, including bone marrow donors, and bone marrow transplant recipients. Normal spectratypes are both complex and stable. The repertoire complexity of marrow recipients correlates with their state of immune function. Contractions and gaps in repertoires are revealed in individuals suffering from recurrent infections associated with T cell impairment. Spectratype analysis is applicable to other studies of specific repertoire skewing such as may be associated with immunodeficiency or found at sites of immune activity.

Adult↗
PubMed1994

Effect of T-cell depletion as graft-versus-host disease prophylaxis on engraftment, relapse, and disease-free survival in unrelated marrow transplantation for chronic myelogenous leukemia.

Between January 1988 and March 1993, 48 patients received T-cell-depleted marrow grafts from unrelated donors as treatment for chronic myelogenous leukemia (CML). The median age of the population was 31.7 years (range 5.4 to 53) with 17 of 48 patients greater than 40 years of age. Twenty-seven patients were transplanted in chronic phase, 17 in accelerated phase, and 4 in blast crisis. All patients received a standardized preparative regimen of cyclophosphamide, high-dose cytosine arabinoside, methylprednisolone, and total body irradiation. Marrow grafts were depleted of mature T cells with the alpha beta T-cell receptor antibody T10B9 as graft-versus-host disease (GVHD) prophylaxis. All patients also received posttransplant cyclosporine therapy. Twenty-eight of 48 patients were mismatched with their donors for one or more HLA-A, B, DR, or DQ loci by either serology or high-resolution oligonucleotide genotyping. Nine of 28 were mismatched at multiple HLA loci. Durable engraftment was achieved in 94% (45/48) of patients. The actuarial probability of developing grades II to IV and grades III to IV acute GVHD were 39.6% (95% confidence interval (CI) 26.9 to 53.0) and 8.3% (95% CI 6.1 to 10.9) for the entire cohort. There was no difference in the incidence of grades II to IV acute GVHD between patients receiving matched (36.8%) or mismatched (41.4%) marrow grafts (P = .77). The actuarial probability of relapse at 2 years was 8.8% (95% CI 2.1 to 21.6) for the entire cohort and 18% (95% CI 4 to 41) for patients transplanted in either the accelerated or blast crisis phase (advanced disease). One cytogenetic relapse has occurred among patients transplanted in the chronic phase. The probability of disease-free survival at 2 years was 52% (95% CI 24 to 70) for patients transplanted in chronic phase and 46% (95% CI 25 to 73) for patients transplanted with advanced disease. No difference in disease-free survival was observed between patients receiving matched (49%) or mismatched (51%) marrow grafts (P = .90). This study shows that patients receiving unrelated T-cell-depleted marrow grafts for CML can achieve durable engraftment with a low incidence of severe GVHD and apparent preservation of graft-versus-leukemia reactivity. These data also suggest that T-cell depletion may allow patients who might otherwise experience unacceptable toxicity from GVHD-related complications caused by older age or increased HLA disparity to benefit from unrelated marrow grafts.

Adolescent↗
PubMed1990

Both ongoing suppression and clonal elimination contribute to graft-host tolerance after transplantation of HLA mismatched T cell-depleted marrow for severe combined immunodeficiency.

Lymphocytes from children with severe combined immunodeficiency who had been immunologically reconstituted with haploidentical T cell-depleted bone marrow were analyzed with regard to their immunologic recognition of donor, host, or third party alloantigens. When compared with freshly isolated donor lymphocytes, the engrafted donor cells exhibited markedly reduced to absent responses toward host Ag in primary or secondary MLC and cell-mediated lympholysis assays. However, under limiting dilution conditions, cytotoxic responses to host Ag could be demonstrated, indicating that small numbers of host reactive cells were present, although down-regulated at high responder cell doses. These results are consistent with prior observations in limiting dilution cultures that indicate that cells with the potential to lyse autologous target cells exist in the peripheral blood of all normal individuals. The number of host reactive cells present in these patients is significantly less than that present in cells isolated directly from the marrow donors, and is also less than the number of autocytotoxic cells normally seen in peripheral blood. Together, these observations indicate that two mechanisms contribute to donor host tolerance in these patients. The majority of host reactive cells appear to have undergone clonal deletion or inactivation, whereas the small residual host-reactive population appears to be under ongoing immunoregulatory control.

Bone Marrow Transplantation↗
PubMed1989

Characterization of B cells in severe combined immunodeficiency disease.

The circulating lymphoid cells of eight consecutive untreated infants with severe combined immunodeficiency disease (SCID) with B cells were analyzed for surface marker expression and function. The B cells of these children expressed sIg, HLA-DR, CD19 (B4), CD20 (B1), CD21 (B2), Leu-8, and lacked expression of CD10 (CALLA), as do normal peripheral blood B lymphocytes. SCID B cells also expressed antigens that are normally absent or present on only a minor subset of circulating adult B lymphocytes, including CD1c (M241), CD38 (OKT10), CD23 (PL13), with or without concomitant CD5 (Leu-1) expression. The B cells of these children were capable of proliferating in vitro when stimulated with Staphylococcus aureus Cowan I. However, in the presence of pokeweed mitogen, S. aureus Cowan I, and normal T cells, the sIg+ cells of these children produced only IgM. Studies performed on normal B cells obtained from cord blood, young children, and adults reveal that whereas cord blood B cells are predominantly CD1c, CD38, and CD23 positive, B-cell expression of these antigens decreases with age. Cord blood B cells, similar to SCID B cells, produce only IgM when stimulated in vitro with pokeweed mitogen and S. aureus Cowan I. Based on these observations, we hypothesize that SCID B cells represent a population of B cells present during normal B-cell ontogeny which becomes a minor subset when an individual develops full immunologic competence.

Antibodies, Monoclonal↗
PubMed1987

M241 (CD1) expression on B lymphocytes.

The human thymus leukemia-like antigens (CD1a-c) consist of three similar glycoproteins found on subpopulations of normal thymocytes, T cell acute leukemias, and cutaneous dendritic cells. The CD1c antigen recognized by the M241 monoclonal antibody was detected on the circulating mononuclear cells of three children with severe combined immunodeficiency disease (SCID). Two-color immunofluorescence analysis demonstrated that M241 expression (43 to 95%) was limited to cells expressing the B cell-restricted antigens B4 (CD19), B1 (CD20), and surface immunoglobulin. To confirm M241 expression on normal cells of the B lineage rather than aberrant expression limited to SCID B cells, its expression was demonstrated serologically and biochemically on purified B cells from spleen, tonsil, and peripheral blood. Parallel analyses with monoclonal antibodies NA1/34 and 4A76 demonstrated that the CD1a and CD1b molecules were negative on all B cells that were studied. It has been hypothesized that the CD1 molecules represent the human counterpart of the murine thymus leukemia antigens due to their similar size, limited tissue distribution, and association with beta 2-microglobulin. This study suggests that a subset of CD1 antigens detected by M241 (CD1c) may represent a human analog of a murine Qa antigen due to its extended distribution on normal peripheral B cells.

Antibodies, Monoclonal↗
PubMed1986

Evaluation of HLA-haplotype disparate parental marrow grafts depleted of T lymphocytes by differential agglutination with a soybean lectin and E-rosette depletion for the treatment of severe combined immunodeficiency.

The factors that impact upon successful bone marrow transplantation leading to immunologic reconstitution in severe combined immune deficiency (SCID). Wiskott-Aldrich syndrome, and in other lethal congenital immunodeficiencies are reviewed. Evidence is presented that graft-versus-host disease (GVHD) can be abrogated by the depletion of T cells, even from histoincompatible marrow grafts. However, graft resistance or restricted immune reconstitution has been observed with significant frequency. The bases for T cell reconstitution and limitations in B cell humoral immune recovery in the postgrafting period are reviewed, together with emerging evidence that pretransplant cytoreduction might obviate some of these problems.

Agglutination Tests↗
PubMed1983

A critical analysis of paternity determination using HLA and five erythrocyte antigen systems.

Five hundred and thirty-seven cases of disputed paternity in North Carolina were tested for five erythrocyte polymorphisms, HLA antigens, or both. The data were analyzed to evaluate the ability of the tests to exclude the alleged father or to include the alleged father as the biological father. Incompatibility between the phenotypes of the alleged father, and those of the mother and child, were found in 40.6% of black males and 30.3% of white males (P less than 0.005). The rates of exclusion appeared to vary between countries in which the cases originated, although the significance of the differences could not be determined because of the small sample size. Using a Bayesian approach and 0.5 as the prior probability of paternity, we calculated the posterior probability of paternity for HLA and five erythrocyte systems combined as well as for HLA and erythrocyte systems separately. The probability of paternity values based on the combined HLA and RBC tests exceeded 95% in 299 of the 345 nonexcluded cases as compared to only 218 cases based on HLA tests alone and 36 cases based on erythrocyte tests alone. We conclude that in approximately 10% of paternity cases in the population served by this laboratory, the information obtained is inconclusive. To resolve these cases, additional polymorphisms and/or a panel of genetic tests systems which can provide greater than 95% probability of exclusion is required.

Bayes Theorem↗