CD46 in innate and adaptive immunity: an update.

CD46 was discovered in 1986 during a search for novel C3b-binding proteins. CD46 is expressed ubiquitously and functions as a co-factor in the factor I-mediated proteolytic cleavage of C3b and C4b. Its vital role in preventing complement deposition on host tissue is underpinned by the fact that deficiency of CD46 is a predisposing factor for numerous disease conditions arising from complement-mediated 'self-attack'. However, in the last 10 years, it has become apparent that CD46 is also heavily involved in a new and somewhat surprising functional aspect of the complement system: the down-modulation of adaptive T helper type 1 (Th1) immune responses by regulating the production of interferon (IFN)-γ versus interleukin (IL)-10 within these cells. Specifically, this latter function of CD46 is a tantalizing discovery - it may not only have delivered the explanation as to why so many pathogens use and abuse CD46 as cell entry receptor but clearly has important clinical implications for the better understanding of Th1-mediated disease states and novel therapeutic approaches for their amelioration. Here, we summarize and discuss the current knowledge about CD46 and its expanding roles in the immune system.

DNA repair by polymerase delta in Saccharomyces cerevisiae is not controlled by the proliferating cell nuclear antigen-like Rad17/Mec3/Ddc1 complex.

DNA damage activates several mechanisms such as DNA repair and cell cycle checkpoints. The Saccharomyces cerevisiae heterotrimeric checkpoint clamp consisting of the Rad17, Mec3 and Ddc1 subunits is an early response factor to DNA damage and activates checkpoints. This complex is structurally similar to the proliferating cell nuclear antigen (PCNA), which serves as a sliding clamp platform for DNA replication. Growing evidence suggests that PCNA-like complexes play a major role in DNA repair as they have been shown to interact with and stimulate several proteins, including specialized DNA polymerases. With the aim of extending our knowledge concerning the link between checkpoint activation and DNA repair, we tested the possibility of a functional interaction between the Rad17/Mec3/Ddc1 complex and the replicative DNA polymerases alpha, delta and epsilon. The analysis of sensitivity response of single and double mutants to UVC and 8-MOP + UVA-induced DNA damage suggests that the PCNA-like component Mec3p of S. cerevisiae neither relies on nor competes with the third subunit of DNA polymerase delta, Pol32p, for lesion removal. No enhanced sensitivity was observed when inactivating components of DNA polymerases alpha and epsilon in the absence of Mec3p. The hypersensitivity of pol32Delta to photoactivated 8-MOP suggests that the replicative DNA polymerase delta also participates in the repair of mono- and bi-functional DNA adducts. Repair of UVC and 8-MOP + UVA-induced DNA damage via polymerase delta thus occurs independent of the Rad17/Mec3/Ddc1 checkpoint clamp.

DNA repair by polymerase delta in Saccharomyces cerevisiae is not controlled by the proliferating cell nuclear antigen-like Rad17/Mec3/Ddc1complex

DNA damage activates several mechanisms such as DNA repair and cell cycle checkpoints. The Saccharomyces cerevisiae heterotrimeric checkpoint clamp consisting of the Rad17, Mec3 and Ddc1 subunits is an early response factor to DNA damage and activates checkpoints. This complex is structurally similar to the proliferating cell nuclear antigen (PCNA), which serves as a sliding clamp platform for DNA replication. Growing evidence suggests that PCNA-like complexes play a major role in DNA repair as they have been shown to interact with and stimulate several proteins, including specialized DNA polymerases. With the aim of extending our knowledge concerning the link between checkpoint activation and DNA repair, we tested the possibility of a functional interaction between the Rad17/Mec3/Ddc1 complex and the replicative DNA polymerases alpha, delta and epsilon. The analysis of sensitivity response of single and double mutants to UVC and 8-MOP + UVA-induced DNA damage suggests that the PCNA-like component Mec3p of S. cerevisiae neither relies on nor competes with the third subunit of DNA polymerase delta, Pol32p, for lesion removal. No enhanced sensitivity was observed when inactivating components of DNA polymerases alpha and epsilon in the absence of Mec3p. The hypersensitivity of pol32delta to photoactivated 8-MOP suggests that the replicative DNA polymerase delta also participates in the repair of mono- and bi-functional DNA adducts. Repair of UVC and 8-MOP + UVA-induced DNA damage via polymerase delta thus occurs independent of the Rad17/Mec3/Ddc1 checkpoint clamp.

Psoralen-sensitive mutant pso9-1 of Saccharomyces cerevisiae contains a mutant allele of the DNA damage checkpoint gene MEC3.

Complementation analysis of the pso9-1 yeast mutant strain sensitive to photoactivated mono- and bifunctional psoralens, UV-light 254 nm, and nitrosoguanidine, with pso1 to pso8 mutants, confirmed that it contains a novel pso mutation. Molecular cloning via the reverse genetics complementation approach using a yeast genomic library suggested pso9-1 to be a mutant allele of the DNA damage checkpoint control gene MEC3. Non-complementation of several sensitivity phenotypes in pso9-1/mec3Delta diploids confirmed allelism. The pso9-1 mutant allele contains a -1 frameshift mutation (deletion of one A) at nucleotide position 802 (802delA), resulting in nine different amino acid residues from that point and a premature termination. This mutation affected the binding properties of Pso9-1p, abolishing its interactions with both Rad17p and Ddc1p. Further interaction assays employing mec3 constructions lacking the last 25 and 75 amino acid carboxyl termini were also not able to maintain stable interactions. Moreover, the pso9-1 mutant strain could no longer sense DNA damage since it continued in the cell cycle after 8-MOP + UVA treatment. Taken together, these observations allowed us to propose a model for checkpoint activation generated by photo-induced adducts.

Gene frequencies of the HPA-15 (Gov) platelet alloantigen system in Brazilians.

The HPA-15 (Gov) alloantigen is a biallelic co-dominant system on human platelets, and its allele HPA-15a and HPA-15b differ by an A-->C single nucleotide polymorphism at nucleotide 2108 of the coding sequence resulting in a Tyr682Ser substitution in the mature CD109 glycoprotein. Employing the polymerase chain reaction-restriction fragment length polymorphism technique, we determined the HPA-15 gene frequencies among 276 subjects of distinct Brazilian ethnic groups including, 15 Caucasians, 15 African Brazilians, 15 Orientals, 106 Amazon Xikrin Indians, 31 Amazon Gavioes Indians and 94 blood donors. The calculated HPA-15a and HPA-15b allele frequencies found in Caucasians (0.53/0.47), African Brazilians (0.57/0.43), Orientals (0.57/0.43) and Brazilian blood donors (0.52/0.48) did not differ significantly. However, the HPA-15a and HPA-15b gene frequencies of Xikrin Indians (0.78/0.22) were significantly different from that of all other groups (P < 0.01). The HPA-15a/a, HPA-15a/b and HPA-15b/b genotype frequencies observed in Gavioes Indians were significantly different from those seen in African Brazilians (P = 0.04) and blood donors (P = 0.017). The present data showed that the distribution of the HPA-15 (Gov) system alleles observed among the Brazilian population is quite similar to the distributions already reported among Asian, Canadian and European populations. Moreover, the data indicated differences in the frequency of the HPA-15 system between Amazon Indians and other distinct Brazilian ethnic groups suggesting that Amerindians would be at higher risk of HPA-15 alloimmunization in the need of receiving blood components collected from blood donors of other ethnic groups.

Thermoconditional modulation of the pleiotropic sensitivity phenotype by the Saccharomyces cerevisiae PRP19 mutant allele pso4-1.

The conditionally-lethal pso4-1 mutant allele of the spliceosomal-associated PRP19 gene allowed us to study this gene's influence on pre-mRNA processing, DNA repair and sporulation. Phenotypes related to intron-containing genes were correlated to temperature. Splicing reporter systems and RT-PCR showed splicing efficiency in pso4-1 to be inversely correlated to growth temperature. A single amino acid substitution, replacing leucine with serine, was identified within the N-terminal region of the pso4-1 allele and was shown to affect the interacting properties of Pso4-1p. Amongst 24 interacting clones isolated in a two-hybrid screening, seven could be identified as parts of the RAD2, RLF2 and DBR1 genes. RAD2 encodes an endonuclease indispensable for nucleotide excision repair (NER), RLF2 encodes the major subunit of the chromatin assembly factor I, whose deletion results in sensitivity to UVC radiation, while DBR1 encodes the lariat RNA splicing debranching enzyme, which degrades intron lariat structures during splicing. Characterization of mutagen-sensitive phenotypes of rad2Delta, rlf2Delta and pso4-1 single and double mutant strains showed enhanced sensitivity for the rad2Delta pso4-1 and rlf2Delta pso4-1 double mutants, suggesting a functional interference of these proteins in DNA repair processes in Saccharomyces cerevisiae.

Long-term results of right latissimus dorsi cardiomyoplasty.

BACKGROUND: Initial experimental and clinical studies have shown that cardiomyoplasty using the right latissimus dorsi can improve left ventricular (LV) function early after operation. METHODS: This study presents the long-term clinical results of this procedure. Between March 1991 and November 1992, 16 patients (12 men, 4 women; mean age 57; range 33-77 years) underwent operation. Survivors were evaluated at 6-month intervals for 2 years with right heart catheterization, radionuclide scans, exercise testing, and quality of life questionnaires. RESULTS: The operative mortality was 6% (1/16), but 3 additional patients experienced sudden death within 6 months of operation. Survival was 63% (10/16) at 12 months and 50% (8/16) at 24 months. There were no significant changes in hemodynamic variables at 12 or 24 months after surgery. Left ventricular ejection fraction increased from 26.1 +/- 5.3 to 33.4 +/- 10.3 (p < 0.05) 6 weeks after operation, but was not different from baseline thereafter. The LV end-diastolic volume decreased significantly at 6 months from 306.1 +/- 71 to 249.4 +/- 69 mL (p < 0.01), and remained lower than the preoperative value in subsequent follow-up. Comparison of preoperative LV ejection fraction and LV stroke work index in 24-month survivors (7) and nonsurvivors (9) showed that survivors had better LV function before surgery. Functional status and quality of life were improved. CONCLUSIONS: Long-term results of right latissimus dorsi cardiomyoplasty are comparable to results using the left latissimus dorsi. Overall survival was limited by late sudden death, but survivors had improved functional capacity and stable LV function and size.

The air gun: toy or weapon?

Originally used in warfare, air guns are commonly used in target shooting, as toys, and as "beginner" guns for children. The projectile force of these weapons can rival that of many conventional handguns. Pneumatic weapons pose a serious threat to the pediatric population, and their potential for serious injury must be recognized.

Cutis laxa acquisita associated with multiple myeloma: a case report and review of the literature.

Cutis laxa acquisita is a rare disorder that affects collagen and elastin metabolism. The cause is unknown. Characteristic features include sagging and laxity of the skin, as well as involvement of the lungs, heart, gastrointestinal system, and urogenital tract. Three cases of cutis laxa acquisita have been reported in association with multiple myeloma. Due to the rarity of these disorders, a linkage has been postulated. The clinical and histologic data from the fourth case of cutis laxa acquisita associated with multiple myeloma were compared to the three other cases previously reported in the literature. The relationship between acquired cutis laxa and multiple myeloma is unclear, with only one case revealing possible immune-mediated elastin destruction via IgG immunoglobulin bound to dermal elastin fibers on immunofluoresence examination. No pattern in the clinical courses of the disorder can be seen on review of the four cases with coincident disease. We hypothesize that cutis laxa acquisita represents a paraneoplastic process of multiple myeloma, given the rarity of these diseases. Further investigation is necessary to determine the underlying linkage between these disorders. We suggest that serum and urine protein electrophoresis results be obtained in patients presenting with cutis laxa acquisita to screen for multiple myeloma given this association.

Tattoo pigment mimicking metastatic malignant melanoma.

BACKGROUND: The benefits of elective lymph node dissection (ELND) in the treatment of melanoma remain controversial, however, it may be beneficial in some patients. Tattoo pigment from decorative tattoos may migrate to the regional lymph nodes. In patients who develop malignant melanoma and who have been tattooed, this pigment may clinically mimic metastatic disease. OBJECTIVE: We wish to alert clinicians that pigment from tattoos may migrate to the regional lymph nodes. In the unusual instance of a tattooed patient who develops malignant melanoma, when undergoing ELND, surgeons should rely on histologic confirmation of metastatic disease before altering operative plans. METHODS: ELND for malignant melanoma, in a patient with a history of decorative tattoos that had been removed by dermabrasion, was performed. Black lymph nodes that clinically resembled metastatic disease were identified. Subsequent histologic examination revealed normal lymph node architecture with a heavy collection of black pigment. Mass spectrophotometry showed this pigment to be consistent with tattoo dye. RESULTS: A patient who had undergone dermabrasion for removal of decorative tattoos developed malignant melanoma in the same extremity. Clinically suspicious black lymph nodes were identified during ELND. Histologic examination did not reveal metastatic disease. Additional therapy was not considered intra- or postoperatively even though the clinical suspicion of metastatic disease was high. The patient was not subjected to any unnecessary emotional or physical distress pending histologic confirmation. CONCLUSIONS: Tattoo pigment in the lymph nodes may clinically mimic metastatic melanoma. Histologic confirmation of metastatic disease should always be obtained before additional therapy is considered.

Regional effects of aortomyoplasty in acute ischemia.

BACKGROUND: Aortomyoplasty is a technique for achieving autogenous diastolic counterpulsation. This experiment was designed to determine if aortomyoplasty using conditioned latissimus dorsi muscle could improve regional myocardial function during coronary ischemia. METHODS: Six mongrel dogs underwent a staged operation in which the left latissimus dorsi was conditioned in situ for 4 weeks, then wrapped around the descending aorta and stimulated during diastole with each cardiac contraction. Regional ischemia was caused by occlusion of the left anterior descending coronary artery. Regional function was measured with somomicrometry in the region of ischemia and in a control area. An intraaortic balloon pump was inserted for comparison with aortomyoplasty performance. RESULTS: Coronary artery occlusion caused a significant decrease in the percentage of regional shortening (14.2 +/- 7.9 to -2.2 +/- 4.0; p = 0.001) and thickening (11.9 +/- 4.6 to -5.8 +/- 3.3; p < 0.001). Aortomyoplasty improved regional motion in both percentage shortening (-2.2 +/- 4.0 to 2.3 +/- 3.7; p = 0.008) and thickening (-5.8 +/- 3.3 to 2.8 +/- 1.9; p < 0.001). The intraaortic balloon pump also improved percentage shortening (-3.7 +/- 2.0 to 0.7 +/- 1.9; p = 0.01) and thickening (-5.0 +/- 2.8 to 2.4 +/- 3.8; p < 0.001), and was not significantly different than aortomyoplasty. CONCLUSIONS: These data show that aortomyoplasty has beneficial effects on ischemic left ventricular contractility, and may therefore be useful for treating inoperable coronary artery disease.

Coccidioidomycosis: the other great imitator.

A "great imitator," like the perhaps more familiar syphilis and tuberculosis, coccidioidomycosis has a wide variety of clinical presentations. A recent dramatic surge in the incidence of this saprobe increases the likelihood that clinicians will encounter an infected patient. Although rare, the disseminated form of the disease is potentially fatal. Vigilance and familiarity with the many faces of this pathogen will permit early detection and treatment. We present two cases of disseminated coccidioidomycosis and briefly review this increasingly common fungal infection.

Topical capsaicin for treatment of hemodialysis-related pruritus.

Pruritus is a significant problem for many patients undergoing long-term hemodialysis. Topical capsaicin depletes and prevents the reaccumulation of substance P in peripheral sensory neurons. Substance P functions in the transmission of pain and probably itch sensations. An open-label, uncontrolled trial and a double-blind, vehicle-controlled trial were conducted to evaluate the efficacy and safety of capsaicin 0.025% cream in the treatment of localized areas of pruritus in patients undergoing long-term hemodialysis. Eight of nine evaluable patients in the open-label trial reported marked relief or complete resolution of itching during the study period, and two of five evaluable patients in the double-blind trial reported complete resolution of itching in the capsaicin-treated arm with no or minimal improvement in the vehicle-treated arm. Twelve patients in the open-label trial and two in the double-blind trial were unevaluable. No serious treatment-related adverse reactions occurred.

Streptokinase dissolution of a right atrial thrombus associated with a temporary pacemaker.

Thrombosis of intravascular catheters is a well-recognized and potentially serious complication, which has been treated successfully with thrombolytic agents. A routine echocardiogram in a patient with a temporary transvenous pacemaker demonstrated a large thrombus attached to the pacing electrode. This was dissolved successfully and uneventfully with high-dose intravenous streptokinase therapy. To our knowledge, this is the first report of the successful lysis of a right atrial thrombus complicating a temporary transvenous pacemaker.

Temporal relationships among immunologic alterations in a guinea pig model of thermal injury.

Temporal relationships among various humoral and cellular alterations of host defense mechanisms were investigated in a guinea pig model of thermal injury during three weeks after burning. Reduction in serum concentration of C3 and fixation of C3 on Pseudomonas aeruginosa, presence of activated C3 in plasma, and elevations in levels of 6-ketoprostaglandin F1 alpha and thromboxane B2 in wound fluid were observed at 3-6 hr after burning. These alterations were accompanied by reduction in intrinsic bactericidal activity of polymorphonuclear neutrophils (PMNs) against P. aeruginosa, suppression of bactericidal activity of PMNs by serum, and decreased blood clearance of P. aeruginosa. All parameters returned to normal values by seven to nine days after burning. Proliferative responses of splenic lymphocytes to T cell mitogens were depressed at four days after burning and were maximally reduced at eight days. These data support the concept that there is a continuum of immunologic alterations resulting from thermal injury and that consumption of complement and increase in arachidonic acid metabolism are early events.