De Novo Donor-Specific HLA Antibodies Are Associated With Rapid Loss of Graft Function Following Islet Transplantation in Type 1 Diabetes

Outcomes after islet transplantation continue to improve but etiology of graft failure remains unclear. De novo donor-specific human leukocyte antigen (HLA) antibodies (DSA) posttransplant are increasingly recognized as a negative prognostic marker. Specific temporal associations between DSA and graft function remain undefined particularly in programs undertaking multiple sequential transplants. Impact of de novo DSA on graft function over 12 months following first islet transplant was determined prospectively in consecutive recipients taking tacrolimus/mycophenolate immunosuppression at a single center. Mixed-meal tolerance test was undertaken in parallel with HLA antibody assessment pretransplant and 1-3 months posttransplant. Sixteen participants received a total of 26 islet transplants. Five (19%) grafts were associated with de novo DSA. Five (31%) recipients were affected: three post-first transplant; two post-second transplant. DSA developed within 4 weeks of all sensitizing grafts and were associated with decreased stimulated C-peptide (median [interquartile range]) at 3 months posttransplant (DSA negative: 613(300-1090); DSA positive 106(34-235) pmol/L [p = 0.004]). De novo DSA directed against most recent islet transplant were absolutely associated with loss of graft function despite maintained immunosuppression at 12 months in the absence of a rescue nonsensitizing transplant. Alemtuzumab induction immunosuppression was associated with reduced incidence of de novo DSA formation (p = 0.03).

Vimentin antibody production in transplant patients and immunomodulatory effects of vimentin in-vitro

We investigated the presence of antibodies to vimentin in 150 patients awaiting transplant, (50 kidney, 50 liver and 50 thoracic) and in 51 previously transplanted kidney patients whose grafts had failed. Patients with primary end stage thoracic or kidney disease did not have increased levels of vimentin antibodies, but those with primary liver failure and those with kidney graft failure did. Those with kidney graft failure were more likely to form vimentin antibodies if the patient was HLA-DQ2 positive (p=<0.001). Further to this, we observed antibody mediated rejection in five HLA-DQ2 positive re-transplant patients where no other antibodies were identified. We investigated the effects of vimentin protein on cytokine production in phytohaemagglutinin stimulated and unstimulated peripheral blood mononuclear cells. When exposed to vimentin at low levels there was increased production of IL-10. When cultures were stimulated, there was a decrease in IL-10, IL-2 and IFN-gamma production and a large increase in IL-4 production (p=0.028) compared to the controls. These results suggest that under normal conditions exposure to vimentin can lead to regulation of the immune response. However, if the immune system is active, exposure to vimentin can enhance Th-2 immunity.

Donor-specific HLA antibodies in paediatric cardiac transplant recipients are associated with poor graft survival

There is increasing evidence that DSA are associated with poor graft survival, although there are little data in children. We aimed to describe the incidence of DSA in this group and to determine correlation with graft survival. HLA antibodies were analysed in 59 paediatric cardiac transplant recipients. Mean age 10.4 (0.7-18.5) yr, mean time post-transplant 5.1 (0.3-17.3) yr. Antibody detection/identification was performed on the Luminex platform with subsequent identification using Lifescreen Identification kits/One-Lambda Single antigen kits. Forty patients (69%) had no HLA antibodies. DSA were found in four (7%). One had transient Class I antibodies and normal cardiac function. The other three had persistent Class II antibodies (two subsequently required re-transplantation, the third had cardiac failure due to CAV). Non-DSA were found in 15 (25%), all with normal graft function and without rejection. There was no difference in function or CAV prevalence between those with non-DSA and those without antibodies. HLA DSA is uncommon in paediatric cardiac allograft recipients but, if persistent, suggests poorer prognosis. In our series, antibodies to HLA class II on donor tissue were associated with increased graft loss. Routine screening and regular testing are recommended.

The HLA system: immunobiology, HLA typing, antibody screening and crossmatching techniques

The Human Leukocyte Antigen (HLA) system plays a critical role in regulating the immune response. As a consequence of its role in immune regulation and exquisite polymorphism, the HLA system also constitutes an immunological barrier which must be avoided or otherwise overcome in clinical transplantation. This introductory review provides a brief summary of the immunobiology of the HLA system and methodology for HLA typing, antibody screening and patient-donor cross-matching. This constitutes a basis for consideration of the importance of these procedures in the system-specific reviews which follow.

Effects of teacher attention on attending behavior of two boys at adjacent desks

The effects of teacher attention on the attending behavior of two boys seated at adjacent desks were investigated. Baseline records were obtained of the appropriate attending behavior of two boys who were described as the most disruptive pupils in a second-grade classroom of a poverty area school. During the first experimental phase, the teacher systematically increased the amount of attention for appropriate attending in one of the pair, Edwin. This resulted in a dramatic increase in his attending rate and a lesser, though significant, increase in attending behavior of the second boy, Greg. During the second experimental phase, systematic attention for attending was instituted for Greg and was discontinued for Edwin. This resulted in further increases in attending by Greg and a reduction in attending by Edwin. A brief withdrawal of reinforcement for attending in both Greg and Edwin reduced attending levels for both. Following this reversal appropriate attending for both boys was systematically reinforced and attending returned to high levels.

Transmission dynamics of malaria in four selected ecological zones of Nigeria in the rainy season

BACKGROUND

Two of the problems of malaria parasite vector control in Nigeria are the diversity of Anopheline vectors and large size of the country. Anopheline distribution and transmission dynamics of malaria were therefore compared between four ecotypes in Nigeria during the rainy season.

METHODS

Polymerase chain reaction (PCR) was used in molecular identification after morphological identification microscopically. Enzyme linked immunosorbent assay (ELISA) was used for the blood meal analysis and sporozoite detection.

RESULTS

Five species were identified out of 16,410 anophelines collected. An. gambiae s.s made up approximately 29.2%-36.6% of the population in each zone. All five species acted as vectors for P. falciparum. An. gambiae s.s had the highest sporozoite rate. The most infected mosquitoes were found in the rain forest. More blood meals were taken from bovids, except the savannah forest, where 73.3% were on humans and Human Blood index (HBI) was 57.3%. The Entomological inoculation rate (EIR) was a mean of 13.6 ib/p but was highest in the rainforest zone.

CONCLUSIONS AND LIMITATIONS

This study demonstrates the complex distribution of anophelines and the considerable variations in the intensity of malaria transmission in Nigeria. We highlight the need to consider diverse epidemiological situations when planning countrywide control programmes.

My approach to cardiothoracic transplantation and the role of the histocompatibility and immunogenetics laboratory in a rapidly developing field

Cardiothoracic transplantation presents specific challenges. The lack of long-term replacement therapy (such as dialysis for kidney patients) creates a more urgent situation than for other forms of transplantation, necessitating a different approach. This review looks at ways in which the challenges are being met and the integral role of the histocompatibility and immunogenetics laboratory.

MHC-correlated odour preferences in humans and the use of oral contraceptives

Previous studies in animals and humans show that genes in the major histocompatibility complex (MHC) influence individual odours and that females often prefer odour of MHC-dissimilar males, perhaps to increase offspring heterozygosity or reduce inbreeding. Women using oral hormonal contraceptives have been reported to have the opposite preference, raising the possibility that oral contraceptives alter female preference towards MHC similarity, with possible fertility costs. Here we test directly whether contraceptive pill use alters odour preferences using a longitudinal design in which women were tested before and after initiating pill use; a control group of non-users were tested with a comparable interval between test sessions. In contrast to some previous studies, there was no significant difference in ratings between odours of MHC-dissimilar and MHC-similar men among women during the follicular cycle phase. However, single women preferred odours of MHC-similar men, while women in relationships preferred odours of MHC-dissimilar men, a result consistent with studies in other species, suggesting that paired females may seek to improve offspring quality through extra-pair partnerships. Across tests, we found a significant preference shift towards MHC similarity associated with pill use, which was not evident in the control group. If odour plays a role in human mate choice, our results suggest that contraceptive pill use could disrupt disassortative mate preferences.

MHC-assortative facial preferences in humans

Individuals tend to choose mates who are sufficiently genetically dissimilar to avoid inbreeding. As facial attractiveness is a key factor in human mate preference, we investigated whether facial preferences were related to genetic dissimilarity. We asked female volunteers to rate the attractiveness of men from photographs and compared these results with individual genotypes at the major histocompatibility complex (MHC). In contrast to previously reported preferences based on odour, we found a non-significant tendency for women to rate MHC-similar faces as more attractive, suggesting a preference for cues to a self-similar MHC in faces. Further analysis revealed that male faces received higher attractiveness scores when rated by women who were MHC-similar than by MHC-dissimilar women. Although unexpected, this MHC-similar facial preference is consistent with other studies documenting assortative preferences in humans, including for facial phenotype.

A case of acute humoral rejection in liver transplantation: successful treatment with plasmapheresis and mycophenolate mofetil

We present a case of a 23-year-old female who underwent orthotopic liver transplantation (OLTx) for biliary atresia, 22 years after a failed Kasai operation. Unusually, her postoperative course was complicated by severe acute humoral rejection. In this case report, we discuss her management as well as the role of plasmapheresis in treating allograft dysfunction secondary to acute humoral rejection in liver transplant patients.

The tapeworm Ligula intestinalis (Cestoda: Pseudophyllidea) inhibits LH expression and puberty in its teleost host, Rutilus rutilus

The tapewormLigula intestinalisoccurs in the body cavity of its cyprinid second intermediate host, in this study the roachRutilus rutilus, and inhibits host gonadal development. The mechanism by which infected fish are prevented from reproducing is unknown. Comparison of parameters, such as body length and weight, and condition factor and age, between infected and uninfected individuals, indicated only minor effects of parasitism on growth and condition. In contrast, seasonal gonadal development, as observed in uninfected fish, did not occur in infected fish, and gonads remained small and blocked at the primary oocyte stage in female roach. As immature ovaries and testes are still present, the parasite is presumed to act upon the brain–pituitary–gonadal axis of the fish to inhibit further development of reproductive organs. We investigated theLigula/fish interaction at the level of the pituitary gland by determination of gonadotrophin (LH) content using a heterologous RIA for carp (Cyprinus carpio) LHβ subunit. The results indicated that the pituitary glands of infected roach contained approximately 50% less LH than non-infected fish. After the cloning and sequencing of roach LHβ subunit, we measured roach LHβ mRNA levels by real-time RT-PCR. A corresponding 50% reduction in LHβ mRNA pituitary levels was determined. These results reflect a significant and measurable effect of parasitism on the pituitary gland, and lend support to the hypothesis that excretory/secretory products released from the parasite interact with the brain–pituitary–gonadal axis of the fish host and thus inhibit gonadal development.

Anti-vimentin Antibody Detection in Recipients of Heart-Beating and Non–Heart Beating Donor Kidneys

Alternative donor sources include non-heart-beating donors (NHBDs). There donors have been exposed to significant ischemia, so that it is common to utilize machine perfusion to either improve the organs or at least assess their viability. Both prolonged warm ischemia and machine perfusion can potentially damage the vascular endothelium, thereby exposing vimentin to antigenic recognition. The aim of this study was to determine whether anti-vimentin antibodies could be detected in the blood of renal transplant recipients at specific time points after transplant and whether they could be related to the donor source. Fifty-one recipients of NHBD kidneys were compared to 52 recipients of heart-beating donor (HBD) kidneys. All recipients had similar anti-vimentin levels pretransplant. However, at 1 month those kidneys from Maastricht category II NHB donors showed significantly higher levels. At 6 months both Maastricht category II and category III NHB donor recipients displayed significantly higher levels than recipients of HBD kidneys.

Do Recipients of Kidneys From Donors Treated With Streptokinase Develop Anti-streptokinase Antibodies?

Streptokinase is used for preflush for non-heart-beating donors (NHBDs) in our center. The aim of this study was to evaluate whether the use of thrombolytic streptokinase results in the production of anti-streptokinase antibodies in the recipients after renal transplantation. Recipient sera taken prior to and at 1 and 6 months posttransplant were tested for the presence of antibodies to streptokinase using an enzyme-linked immunosorbent assay assay. No differences were detected between a group of 18 recipients who had kidneys from thrombolytic-treated NHBDs and a further group of 18 who received NHBD kidneys without such treatment.

A new HLA-A Allele, HLA-A*6824, identified in three unrelated individuals*

A novel allele, human leukocyte antigen (HLA)-A*6824, has been identified in three unrelated individuals of northwestern European origin in a period of less than 4 months, implying that this allele may be quite common in this population. HLA-A*6824 differs from A*680102 by a single nucleotide change at position 275 in exon 2, which results in a conservative amino acid substitution from lysine to arginine in the peptide-binding groove at codon 68.

Donor CD31 Genotype Impacts on Transplant Complications After Human Leukocyte Antigen-Matched Sibling Allogeneic Bone Marrow Transplantation

Mismatch for the adhesion molecule CD31 (PECAM-1) has been associated in some studies with graft-versus-host disease (GVHD), suggesting a role for CD31 as a minor histocompatibility antigen. We examined polymorphisms of the CD31 (PECAM-1) gene in 74 patients and their human leukocyte antigen-matched sibling donors, comparing CD31 genotype with outcomes of occurrence of GVHD and survival using regression analysis. Polymorphisms in codon 125, 563, and 670 are strongly linked forming conserved haplotypes. Donor CD31 (val/asn/gly) haplotype was associated with acute GVHD (P=0.004, odds ratio 7.5). In addition, donor heterozygosity at codon 563 was significantly associated with worse overall survival after correcting for other known variables by regression modeling. Peptide binding predictions support the hypothesis that CD31 could act as a minor histocompatibility antigen. Assessment for CD31 gene status may be of value in pretransplant assessment of bone marrow transplant recipients and donors for prediction of likely transplant-related complications.

Vimentin Antibodies: A Non-HLA Antibody as a Potential Risk Factor in Renal Transplantation

Chronic allograft rejection is the major problem encountered in solid organ transplantation and is the end point of several complex processes. A number of recent studies show both alloimmune and autoimmune responses may have roles to play. The importance of HLA antibodies in transplantation is well documented, but despite the introduction of very sensitive HLA screening assays, antibody-mediated allograft rejection still occurs without detectable HLA antibodies. The target for antibody-mediated allograft rejection in these circumstances remains elusive, perhaps due to the variety of potential targets presented on endothelial cells. Recent studies identifying C4d and immunoglobulin deposits in patients undergoing late allograft loss provide evidence that chronic rejection involves humoral as well as cellular components. Several endothelial cell antigens that might be important in chronic rejection have been suggested, including MHC class I chain-related genes; Lewis; and the intermediate filament protein, vimentin. Vimentin is an ideal candidate antigen for antibody-mediated rejection as it is found in endothelial cells and is exposed to the immune system following surgery or by chronic allograft rejection due to endothelial cell breakdown, where the development of antibodies may cause further damage. We have developed a flow cytometric assay for the detection of antibodies to vimentin and have investigated whether HLA or vimentin antibodies are present in renal transplant recipients undergoing chronic rejection.

Interactions between malaria and mosquitoes: the role of apoptosis in parasite establishment and vector response to infection

Malaria parasites of the genus Plasmodium are transmitted from host to host by mosquitoes. Sexual reproduction occurs in the blood meal and the resultant motile zygote, the ookinete, migrates through the midgut epithelium and transforms to an oocyst under the basal lamina. After sporogony, sporozoites are released into the mosquito haemocoel and invade the salivary gland before injection when next the mosquito feeds on a host. Interactions between parasite and vector occur at all stages of the establishment and development of the parasite and some of these result in the death of parasite and host cells by apoptosis. Infection-induced programmed cell death occurs in patches of follicular epithelial cells in the ovary, resulting in follicle resorption and thus a reduction in egg production. We argue that fecundity reduction will result in a change in resource partitioning that may benefit the parasite. Apoptosis also occurs in cells of the midgut epithelium that have been invaded by the parasite and are subsequently expelled into the midgut. In addition, the parasite itself dies by a process of programmed cell death (PCD) in the lumen of the midgut before invasion has occurred. Caspase-like activity has been detected in the cytoplasm of the ookinetes, despite the absence of genes homologous to caspases in the genome of this, or any, unicellular eukaryote. The putative involvement of other cysteine proteases in ancient apoptotic pathways is discussed. Potential signal pathways for induction of apoptosis in the host and parasite are reviewed and we consider the evidence that nitric oxide may play a role in this induction. Finally, we consider the hypothesis that death of some parasites in the midgut will limit infection and thus prevent vector death before the parasites have developed into mature sporozoites.

Transfusion-related acute lung injury caused by two donors with anti-human leucocyte antigen class II antibodies: a look-back investigation

Transfusion-related acute lung injury (TRALI) is considered as one of the most important complications of blood transfusion. Previous look-back investigations have revealed unrecognized cases. We report two cases of TRALI in brief and the outcomes of transfusion in the recipients of previous components from the implicated donors. This look-back investigation was a retrospective case-note study assessing whether there were any untoward events associated with the previous transfusions. 18 patients were identified as having received a blood component transfusion from one of the two donors with anti-human leucocyte antigen (HLA) antibodies to antigens occurring frequently in the local population. One of the five patients receiving a unit of fresh frozen plasma had an evidence of TRALI, which was not diagnosed at the time. A second patient, who had been HLA typed and who carried a full match of antigens for the antibody specificities of the plasma received, had no evidence of a reaction. There were no documented reactions in 13 recipients of red cells in optimal additive (OA) solution. Cases of TRALI may go unrecognized. Not all patients with antibody/antigen concordance will develop clinical signs. Red cells in OA solution from donors with anti-HLA antibodies appear to have a low risk of causing clinically evident lung damage.

CAMPATH-1M T-cell depleted BMT for SCID: long-term follow-up of 19 children treated 1987-98 in a single center

BACKGROUND

SCID can be cured by BMT. Depletion of mature T cells from BM has enabled HLA non-identical stem-cell transplantation. We report the outcome of 30 patients treated with 37 T-cell depleted BMT procedures using CAMPATH-1M in vitro between 1987-98 in a single center.

METHODS

Immune reconstitution and quality-of-life were assessed in 19 longterm survivors. All but two received pre-transplant conditioning. T- and B-cell chimerism, numbers and function were analyzed during a median follow-up of 5.3 years (range 1.33-12).

RESULTS

The overall engraftment rate was 59%, six children required repeated BMT and the survival rate was 63%. All have donor T cells, 58% normal T-cell numbers and 74% normal T-cell function. Of 17 evaluated, 16 patients (94%) have normal IgM and IgG levels, and production of specific Abs to protein Ags, but only 5/16 (31%) have a good response to pneumococcal polysaccharide. Early and late post-BMT complications were rare and there were no delayed deaths. Only one child continues on long-term i.v. Ig 4-years post-BMT. Eleven children died (37%).

DISCUSSION

CAMPATH-1M T-cell depleted BMT for SCID resulted in 63% survival. Deaths of 11 children were mainly due to pre-existing infections. Seventeen of 19 long-term survivors have normal immune function and good quality-of-life.

The relevance of donor T cell-directed immunoglobulin G in historic sera in the age of flow cytometry

BACKGROUND

Renal transplant recipients with a positive historic cross-match due to donor T cell-directed IgG antibodies are considered to have decreased graft survival, even if their current serum is negative prior to transplantation. With the use of flow cytometric cross-match for testing current sera, false-negative results could be eliminated and the outcome of transplantation in this group of patients could be improved, assuming that immunological memory is effectively controlled with immunosuppression.

METHODS

We reviewed our records to identify those patients who underwent cadaveric renal transplant, with a historic IgG positive cytotoxic T cell cross-match and a current negative flow cytometric T cell cross-match.

RESULTS

Eighteen patients underwent cadaveric renal transplant in the face of a historic IgG positive T cell cross-match and a current negative flow cytometric T cell cross-match. In 14 patients treated with cyclosporine-based immunosuppression the 1-, 2-, and 3-year cumulative graft survival rates were 57, 50, and 43%, respectively. Ten of the 14 patients (71%) ultimately lost their grafts.

CONCLUSIONS

Even with negative flow cytometric cross-match in current serum, a positive historic conventional cross-match suggests a high risk of graft failure.

An HLB-B null allele (B*0808N) caused by a nucleotide deletion in exon 3, found in the family of a bone marrow transplant recipient

We have identified a variant HLA-B allele, B*0808N, segregating through two generations of healthy individuals, whilst HLA typing the family of a bone marrow patient. Serological typing identified a disparity between the father (A1, A3 B7 DR7) and the brother (A1, A2 B56 DR1, DR7) of the patient. Low/medium resolution polymerase chain reaction using sequence-specific primers (PCR-SSP) revealed a B*08 allele undetectable by serological methods. High resolution DNA typing by polymerase chain reaction-sequencing based typing (PCR-SBT), revealed a nucleotide deletion at position 131 (C) in exon 3, the only difference between the new allele and B*0801. The deletion results in a frame shift in the protein coding sequence, introducing a premature termination codon (TGA) in exon 4. Although a B*08 allele is present in these individuals, the deletion prevents correct expression of the antigen on the cell surface.

Identification of an HLA-B7 serological variant and its characterization by sequencing based typing

We have identified an HLA-B*07 variant allele, B*0716, in a Caucasoid cadaver kidney donor. The HLA class I type by polymerase chain reaction using sequence-specific primers (PCR-SSP) was A*01, 32; B*07, 08; Cw*07. Serological typing, using monoclonal and polyclonal anti-HLA antisera, gave disparate results for the B antigens. Monoclonal antibodies identified B7 and B8 antigens but polyclonal antisera recognised only the B8 antigen. PCR using sequencing based typing (PCR-SBT) confirmed the presence of both B*0703 and B*0801 alleles but with a mutation in one of the alleles. The HLA-B*07 allele was isolated by allele-specific PCR and was shown to have a mutation, G-->T, at 292 in exon 2. This mutation changes codon 74, which encodes aspartic acid (GAC) present in all previously identified B*07 alleles, to tyrosine (TAC) in the variant. The serological results suggest that codon 74 is a crucial part of a B7 antigen-specific epitope recognised by tissue typing polyclonal antisera.

Trypanosoma brucei: molecular cloning and stage-regulated expression of a malate dehydrogenase localized to the mitochondrion

African trypanosomes exhibit dramatic developmental changes in carbohydrate and energy metabolism, with cytochrome-mediated respiration playing an important role only in the insect stages. The parasites possess three isozymes of malate dehydrogenase, each of which has a different subcellular localization and, likely, a distinct metabolic role. We have cloned and characterized a cDNA encoding one of these malate dehydrogenases. Epitope tagging and transfection experiments demonstrate that the corresponding protein is localized to the mitochondrion and that an intact amino terminus is required for proper compartmentalization. The abundance of transcript is developmentally regulated, with higher levels in procyclic stage parasites.

The effects of simulated Bier block IVRA on intracompartmental tissue pressure

BACKGROUND

Intravenous regional anesthesia (IVRA) is a useful anesthetic method for closed reduction of fractures. However, IVRA has been associated with an increased incidence of compartment syndrome when treating tibial shaft fractures. The purpose of this study was to measure changes in anterior leg compartment pressures during simulated IVRA.

METHODS

A volunteer study was performed. An indwelling catheter placed in a consistent location between subjects was used to measure tissue pressure. A vinyl leg splint was used for exsanguination followed by thigh tourniquet inflation (300 mmHg). Normal saline (1.5 mL/kg) was injected through the greater saphenous vein (1.0 mL/s). Pressure measurements were obtained before and after tourniquet inflation, at 10 mL increments during saline injection, and intermittently after volume injection with the tourniquet inflated, then deflated.

RESULTS

There was no significant difference in tissue pressure before (2.4 +/- 2.2 mmHg) and after (4.3 +/- 3.7 mmHg) tourniquet inflation (P = 0.11). No significant difference in tissue pressure were found as a function of injected volume (P = 0.62), as a function of time following saline injection during tourniquet inflation (P = 0.08), and after tourniquet deflation (P = 0.16).

CONCLUSIONS

We conclude that in the normal atraumatic limb, simulated IVRA using normal saline does not increase tissue pressure within the anterior leg compartment.

A novel variant of the beta-subunit of the amiloride-sensitive sodium channel in African Americans

The amiloride-sensitive sodium channel is responsible for the rate-limiting step of sodium reabsorption in the distal renal tubule, and thus may play a key role in the maintenance of sodium balance and blood pressure. In this study, a genetic variant that results in a change of threonine to methionine at amino acid 594 (T594 M) in the carboxy-terminus of the beta-subunit of the amiloride-sensitive sodium channel has been identified. This variant was present in 6.1% of African-American subjects (N = 231) but was not seen in Caucasians (N = 192). Whole cell voltage clamp of B-lymphocytes from individuals with the T594 M variant showed similar basal membrane slope conductance, compared with the wild-type but increased response to cAMP analog.

Trypanosoma congolense: developmental regulation of protein kinases and tyrosine phosphorylation during the life cycle

In higher eukaryotes, key steps in the control of growth and proliferation are regulated by protein phosphorylation. However, little is known about the role of protein phosphorylation in the developmental cycles of pathogenic protozoa. In Trypanosoma brucei, only the bloodform and procyclic form stages can be obtained in sufficient numbers for biochemical analyses. However, the entire life cycle of Trypanosoma congolense can be generated in vitro, providing sufficient material for analyses of the different developmental stages. The studies reported here provide a series of snapshots documenting the activity of a number of protein serine/threonine kinases and the pattern of tyrosine-phosphorylated proteins throughout the T. congolense developmental cycle. Metacyclic forms and mammalian bloodforms showed similar profiles of protein kinase activity, as did procyclic forms and epimastigotes. Most tyrosine-phosphorylated proteins were shared between all developmental stages, with the exception of a 100-kDa metacyclic-specific species. The developmental changes in molecules involved in protein phosphorylation in the different developmental stages support the concept that changes in protein phosphorylation networks are important correlates of the developmental process in African trypanosomes.