By G. Garik. Amherst College. 2018.
Immortalization of Human B-lymphocytes: Hybridoma Technology The human immune system is a preferred source of antibody-producing B-lymphocytes cheap fluoxetine 10mg online. Vaccinated persons order fluoxetine 20 mg on line, infected, and/or reconvalescent patients represent an ideal source of antigen-primed B-lymphocytes either as a gene donor or for direct immortalization. Although the immortalization of B-lymphocytes is a rather easy technique to per- form, an intrinsic problem is retaining stable antibody production in culture for pro- longed periods. Generally 2 3 weeks after virus infection transformants producing specific antibodies can be detected in the supernatant. However, with continued growth of the culture, specific antibody levels invariably fall and become undetectable after 3 4 months probably owing to the overgrowth of the culture with nonproducing cells. Somatic cell hybridization for the creation of antibodies with prede- termined specificity was first described in 1975 (77). This technology the hybridoma technology revolutionized immunology by allowing production of monoclonal anti- bodies of virtually any specificity. The appli- cation of hybridoma technology to create human antibodies suffered from the variable and often low fusion frequency of hybrids. Furthermore, the isolation and amplifica- tion of antibody-producing B-cells prior to fusion was one of the most critical points. In the following sections the main issues of immortalization of high-producing hybridoma cells will be addressed. In the rodent system, an optimized scheme of immunization can be applied, leading to the enrichment of antigen-stimulated B-lymphoblasts in the spleen, which are activated to enter mitosis concurrently with the fusion partner used for immortalization. By contrast, it is almost impossible to obtain human spleen B-lymphocytes from antigen-primed donors. Because of the lack of accessibility to surgically removed tonsils or spleen cells, alternative techniques have been developed to stimulate naive lymphocytes with the desired antigen outside human body. In Vitro Antigen Priming Techniques of in vitro antigen priming of B-cells are commonly refered to as in vitro immunization. Those include the purification of the lymphocyte population by inactivation or irradi- ation of T-suppressor cells and retaining T-helper cells and macrophages. Often phytohemagglutinin is added to activate T-helper cells secreting the B-cell lymphokines. In vitro immunization procedures for B-cells producing high-affinity IgG have also been described (81). However, none of these complex techniques have achieved widespread industrial application. Amplification of human B-lymphocytes Especially for the immortalization of human B-lymphocytes, very small amounts of cells are often available. The enrichment of the desired population of human B-lymphocytes prior to immortalization can be achieved by two methods. Only a subset of 20% of the total B-cell population is actually immortalized (83,84), whereas a large fraction of activated antibody-producing plasma cells is resistant to transformation (85). This method needs no viral agents, and the cells are subsequently immortalized by fusion. Alternatively, primed B-lymphocytes can be enriched in the cell population by catching the cells with surface-bound, antigen- specific antibody (86). However, only a few myeloma cell lines have been established that are capable of generating human-human hybridomas. Generally, these cell lines show low growth rates with doubling times of 40 60 hours. They also often tend to become senescent, possibly because of their nearly normal diploid chromoso- mal content (89,90). The fusion of human lymphocytes with non-human fusion part- ners generates xenohybridomas preferentially segregating human chromosomes. Since the chromosomal constitution of intraspecific human hybrids is much more stable, human fusion partners for hybrid generation are preferable. Cell morphology obviously correlates with the amount of antibody being pro- duced; abundant rough endoplasmatic reticulum correlates with higher specific expression. It displays rapid cell growth, high cloning efficiency, and a hybridizing effi- 5 ciency of 2 6 clones/10 seeded lymphocytes. Selection Screening and Stabilization for Antibody-Producing Hybridomas After cell fusion, the primary hybrids contain a pool of primary transformants. In these inhomogenous cell pools, only a limited number of hybrids have the capacity to express antibodies of particular speci- ficities. Furthermore, during fusion of the two karyons, the chromosomes capable of antibody expression may be lost. Therefore screening must be combined with an effi- cient selection system that eliminates all lymphocyte/lymphocyte and myeloma/ myeloma primary hybrids. Since only a minor fraction of the lymphocytes are antibody-producing B-lymphocytes, efficient screening procedures for antibody-secreting hybridomas are essential. Using, for exam- ple, human peripheral blood as a source of lymphocytes, it is often not possible to get 7 more than 5 10 lymphocytes with approximately 10% B-cells.
Recently fresh cows are very susceptible to infec- contamination of the milk and milking equipment buy fluoxetine 20 mg without prescription, or tion during herd epidemics 10mg fluoxetine, and errors in transition cow both. Dublin have chronic mas- management often amplify the impact of disease on titis in a percentage of cows infected by this organism. Dublin may be subclinical, and tend to amplify the clinical signs and increase morbidity environmental contamination of quarters has been and mortality. Recording temperatures in apparently shown to be a more likely cause than septicemic spread healthy cows during a herd outbreak may conrm fevers to the udder. Occasional cows have chronic mastitis in some that are about to develop diarrhea or may repre- with Salmonella spp. Concurrent infection with shed organisms and feces from infected cows create Salmonella sp. B, C, or D cause infection and can occur for several Diarrhea and illness caused by salmonellosis are reasons: common in farm workers and families whenever herd 1. It is the veterinarian s obligation to causing fetal infection and death inform clients and workers regarding the public health 2. Endotoxin and other mediator release that cause dangers of salmonellosis and to direct sick farm workers luteolysis via prostaglandin release and apparent or family members to physicians for treatment. High fever or hyperthermia brought about by con- Ancillary Aids and Diagnosis current fever and heat stress during hot weather Hematology and acid-base electrolyte values are valu- Cows may abort at any stage of gestation, but able ancillary aids for individual or valuable cattle but as with many causes of abortion, expulsion of 5- to are seldom diagnostic because of the great variation in 9-month fetuses are most likely to be observed by clinical illness. Isolates should be typed and nation of milk may represent septicemic spread of the antibiotic susceptibility determined. Peracute salmonellosis associated with virulent se- rovars tends to create a neutropenia with degenerative left shift in the leukogram and metabolic acidosis with Na, K, and Cl values all lowered in affected adult cattle. Total protein values initially may be elevated because of severe dehydration but are just as likely to be normal or low because albumin values de- crease quickly as a result of the severe protein-losing enteropathy. Rehydration alone may decrease the lactic acid Sodium, potassium, and chloride tend to be low in and correct the metabolic acidosis. As bicarbonate therapy is absolutely needed for correction mentioned, peracute severe salmonellosis will result in of acidosis in dairy cattle are for severe rumen acidosis, metabolic acidosis as a result of massive uid loss and enterotoxigenic E. Viral catheter damage from head catches, a common prob- isolation should be attempted from the buffy coat of lem with jugular catheters on dairies. Infections normal) administered at 3 to 5 ml/kg followed by 10 to caused by Campylobacter sp. The signicance and disease incidence associated tical method of uid resuscitation in a eld setting. Administration of hypertonic saline into smaller- cosal necrosis in the distal small bowel and colon are diameter veins, such as the auricular vein, may result in present in subacute and chronic cases. When multiple animals however, minimal gross lesions other than hemorrhage merit oral uid administration during an outbreak of and edema may exist within the involved bowel and salmonellosis or any other enteric disease, or if the same enlarged mesenteric lymph nodes. The more acute the equipment is to be used for drenching of other cattle, death, the less likely gross lesions will be observed. Individual patients may be treated aggres- Oral uids and electrolytes may be somewhat help- sively following acid-base and electrolyte assessment. The effective- tensive ancillary workup, and uid therapy is adminis- ness of oral uids may be somewhat compromised by tered empirically. Use of balanced electrolyte solutions malabsorption and maldigestion in salmonellosis pa- such as lactated Ringer s solution is sufcient for most tients but still should be considered useful. Evidence for this phenomenon is sparse ex- succinate is preferred in this instance. Whenever possible, cattle with resent similar risks when treated with antibiotics. Fur- diarrhea should be conned to an area of the barn away ther opposition states that systemic antibiotics prolong from the rest of the herd. Workers must be educated re- the excretion of Salmonellae in the feces and may not garding mechanical transmission of infected feces and shorten the clinical course of purely enteric disease. However, discerning those animals with infection lim- Workers should also be educated regarding the zoonotic ited to the gut wall from those animals with gut wall implications inherent with salmonellosis. Proponents of antibiotic therapy remind us that sal- Prevention and Control monellosis frequently induces bacteremia (although Herd epidemics appear to be increasing in frequency this is most common in calves), thereby risking septice- based on conrmed isolations from multiple cow mic spread of the organism. Clinical differentiation of outbreaks identied from New York and the rest of septicemia versus endotoxemia without septicemia is the northeastern United States. Conditions that con- not easy unless localized infection appears in a joint, tribute to an increasing incidence of epidemic salmo- eye, the meninges, or lungs. In other words, clinicians nellosis include larger herd size, more intensive can seldom accurately predict all salmonellosis patients and crowded husbandry, and the trend for free stall that are truly septicemic. In addition, appropriate anti- barns with loose housing, which contributes to fecal biotic therapy reduces the total number of organisms contamination of the entire premises. Other major shed into the environment by counteracting septicemic contributing factors include the use of feedstuffs that spread that allows all bodily secretions, not just feces, to may be contaminated with Salmonella sp.
Orchitis is an infammation of the testicles cheap 20 mg fluoxetine with amex, The Data which may be caused by any of several bacteria During 2001 cheap fluoxetine 20 mg without prescription, 6,103 primary and secondary or viruses. Orchitis tends to occur in conjunction syphilis cases were reported to state and local health with infections of the prostate or epididymis and, departments in the United States. The The incidence of orchitis is not subject to national 2001 rate for men was 15. Rates have (Table 21) and epididymitis/orchitis not specifed also remained disproportionately high in the South as due to Chlamydia or gonococcus (organism (3. Over 99% of the Background cases were for epididymitis/orchitis not designated Epididymitis, or infammation of the as due to Chlamydia or gonococcus (Table 22); it epididymis, commonly occurs as a complication of appears that clinicians rarely code patients specifcally urethral infection with N. American Native 80 286 (222 351) Region Midwest 800 22 (20 23) 1,120 29 (27 31) 1,400 38 (36 40) Northeast 240 7. The highest rates were seen among African between urban (617 per 100,000) and rural (670 per Americans (87 per 100,000) and persons residing in 100,000) residents. However, because reported cases of gonorrhea pruritis at the end of the urethra (40). In women, Urethritis causes considerable morbidity in urethritis is often observed in association with cystitis terms of pain, suffering, and loss of productivity. Sexually transmitted women averaged about 250,000 in 1996 1997 and infections that may result in urethritis include N. Medical visitsa for epididymitis/orchitis not urethritis cases were classifed as due to Chlamydia or designated as due to Chlamydia or gonococcus, by males gonococcus. Unknown 146 491 (412 571) There was a minimal difference between the rates aThe number of medical visits includes both inpatient visits and outpatient visits; however, most medical visits were outpatient visits. The highest rate was seen among those 25 to 29 1,313 hospitalizations with a urethritis diagnosis, years of age (104 per 100,000). Rates varied greatly by and a progressive decrease in each year of data to geographical region, with the highest rate seen in the 687 hospitalizations in 2000 (Table 27). Again, there was a minimal Medicare hospital outpatient data from 1992 to 1998 difference between the rates for urban (43 per 100,000) yielded counts for cases of urethritis that were too and rural (41 per 100,000) populations. Comparing the frequencies in Tables 28 and 29 indicates that in all three years of study approximately 70% of 266 267 Urologic Diseases in America Sexually Transmitted Diseases Table 27. Risk for chronic departments, which forward the data, without infection is associated with age at infection. As of the and are at increased risk for death from chronic liver same date, more than 467,000 persons reported to disease (31). In 1996, between 3% and 48% of sexually Up to 70% of persons with acute hepatitis B have active young women requesting routine care at previously received care in settings where they could prenatal, family planning, and college health clinics have been vaccinated (e. Other complicated and expensive to manage and therefore symptoms can include painful sexual intercourse, contribute substantially to the overall clinical and lower abdominal discomfort, and the urge to urinate. Urologists should also be aware of heterosexual men who have fewer sexual partners. Estimates of the incidence and prevalence Urologists and other clinicians who see persons of sexually transmitted diseases in the United States. Epididymitis, orchitis, and related shedding, and transmission modes and risks of conditions. Urol Clin complications, counseling, patient education, sex North Am 1984;11:55-64. New York: symptoms and signs and should screen or diagnose McGraw-Hill, 1999:285-312. Projection of the future dimensions and costs of the Urologists and other clinicians should also provide genital herpes simplex type 2 epidemic in the United appropriate counseling, patient education, follow- States. Frequency of acquisition of frst-episode genital infection with herpes simplex virus from available for the clinician through commercial symptomatic and asymptomatic source contacts. Medical care In addition, continued commitment and advocacy for expenditures for genital herpes in the United States. The health and economic burden of genital warts in a set of private health plans in the United States. Standardized health national plan to eliminate syphilis from the United plan reporting in four areas of preventive health care. Lower genital tract infection review with clinical and public health considerations. Sexually transmitted The causal relation between human papillomavirus disease and infertility. New York: McGraw-Hill, cervical cancer among Hispanic and non-Hispanic 1999:1079-1087. New genital human papillomavirus infection in young York: McGraw-Hill, 1999:1133-1143.
These observations suggest that the viral load set point (and the corresponding rate of disease progression) for an individual may be determined primarily by host factors that control viral replication fluoxetine 20 mg with mastercard, rather than the virologic characteristics of the original inoculum discount fluoxetine 20 mg with mastercard. Although viral vari- ants exist that play a role in some cases, understanding which host effects account for the substantial differences in progression rate between individuals should provide crit- ical insights into the development of new therapeutic targets. However, these rare host phenotypes do not account for the majority of differences in disease progression between individuals. These data suggest that some individuals may become infected (perhaps with a very low viral dose) and mount an immune response sufficient to control the infection prior to the development of an antibody response and established chronic infection. If viral replication could be safely inhibited by tar- geting a host element, this would provide several theoretical advantages. In many instances, host factors in general may be more conserved throughout the population compared with the highly variable and changeable nature of viral proteins. Unlike the rapidly growing and genetically unstable virus quasispecies, host factors would not be predicted to respond quickly to drug pressure in the selection process for drug- resistant variants. Treatment strategies directed at host cells have the potential to be synergistic with antiviral regimens, while minimizing risks of cross-resistance or shared toxicities with drugs from the currently available therapeutic classes. A key unan- swered question is which host factors, if any, can be successfully targeted by thera- peutic interventions. Theoretically, successfully targeting the process of viral entry into host cells would provide certain advantages over drugs that inhibit viral enzymes brought into play in the later steps of the viral life cycle. Unfor- tunately, clinical trials were unsuccessful owing to poor absorption of oral dextran (41,42) and severe adverse events related to intravenous dextran (43). Between 1995 and 1997, a number of investigative groups reported that -chemokines and their derivatives had a significant inhibitory effect on viral replication in vitro (44 47). At the present time, there is insufficient information about the normal role chemokines play in inflamma- tory responses and other physiologic processes. Another theoretical concern is that effectively blocking one of the chemokine receptors may provide selection pressure for the outgrowth of viruses uti- lizing alternative receptors. However, the most straightforward approach to blocking chemokine receptors would be to administer the natural ligands or other small molecules that may serve as compet- itive inhibitors. A smaller derivative, termed T134 (14 amino acids), exhibits greater potency and less cytotoxicity in vitro (59). Synthetic peptides corre- Host Cell-Directed Approaches 225 sponding to segments of gp41 have been shown to disrupt the folding and unfolding of the gp41 tertiary structure necessary for membrane fusion to occur. The second clinical trial of T-20, recently completed, involved 78 subjects enrolled at multiple sites around the United States (61). This trial allowed heavily pretreated patients to add T-20 therapy to their preexisting oral antiretroviral regimens. Thus, these findings provide proof of con- cept that therapeutics targeting a viral entry event can result in safe and clinically meaningful inhibition of viral replication. However, this approach to blocking viral entry is not directly aimed at a conserved host target, as exemplified by the suggestion that selection for resistant viral variants is possible (62,63). Similarly, there appear to be temporary increases in plasma viral load when patients develop opportunistic infections, despite adherence to antiretroviral medications (69,70). Although immunosuppressive therapy is obviously not an attractive option for wide- spread use among patients with acquired T-cell deficiency, preliminary studies have been carried out to explore the potential for limiting T-cell activation as a therapeutic strategy. A pilot study evaluating the effects of low- dose cytotoxic chemotherapy to limit the availability of susceptible target cells is also currently nearing completion. This inverse relationship between blood and inflamed tissues has also been described for other infectious dis- eases. For example, a recent report suggests that the reversal of anergy in patients receiving therapy for tuberculosis corresponds to the release into the bloodstream of tuberculosis-specific T-cells previously sequestered in infected tissues (78). This model is consistent with the general understanding that T-cells are long lived and not rapidly replaced by the body when depleted in other clinical sit- uations (79,80). On the other hand, recent studies suggest that there may be a very gradual return of naive T-cells from unknown regenerative sites after several months of therapy (81). The authors proposed the hypothesis that the higher number of target cells detected following combination therapy in some cases helped to fuel the fire of viral replication. Other experimental approaches have been evaluated in small clinical trials to increase T-cell numbers. This approach would have been difficult to comprehend several years ago, when any attempt to activate viral replica- tion, even transiently, was considered counterproductive. However, after improvements in therapy resulted in dramatic and sustained declines in plasma viral load, more rad- ical approaches seemed justifiable in the quest for viral eradication. Investigational agents that could serve as potent T-cell stimuli have been proposed, but there are uncer- tainties about the relative safety and tolerability of administration. Less toxic possibilities might include growth factors that are capable of stimulating multiple leukocyte cell lines. Although these findings remain to be confirmed and corroborated, the sugges- Host Cell-Directed Approaches 229 tion is that T-cell stimulation has the potential to trigger clearance of the latently infected cell pool. This could occur because cells reactivating viral replication are elim- inated either by virus-mediated destruction or targeted immune surveillance. Most patients who never receive potent antiretroviral therapy eventually succumb to progressive disease and are not able to control viral replication in the long term.
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