Design and implementation of the Americas Hernia Society Quality Collaborative (AHSQC): improving value in hernia care.

PURPOSE: Wide variation in care and costs exists regarding the management of abdominal wall hernias, with unproven benefit for many therapies. This work establishes a specialty society-based solution to improve the quality and value of care delivered to hernia patients during routine clinical management on a national scale. METHODS: The Americas Hernia Society Quality Task Force was charged by the Americas Hernia Society leadership to develop an initiative that utilizes the concepts of continuous quality improvement (CQI). A disease-based registry was created to collect information for CQI incorporating real-time outcome reporting, patient reported outcomes, stakeholder engagement, and collaborative learning methods to form a comprehensive quality improvement effort. RESULTS: The Americas Hernia Society Quality Collaborative (AHSQC) was formed with the mission to provide health care professionals real-time information for maximizing value in hernia care. The initial disease areas selected for CQI were incisional and parastomal hernias with ten priorities encompassing the spectrum of care. A prospective registry was created with real-time analytic feedback to surgeons. A data assurance process was implemented to ensure maximal data quality and completeness. Four collaborative meetings per year were established to meet the goals of the AHSQC. As of the fourth quarter 2014, the AHSQC includes nearly 2377 patients at 38 institutions with 82 participating surgeons. CONCLUSIONS: The AHSQC has been established as a quality improvement initiative utilizing concepts of CQI. This ongoing effort will continually refine its scope and goals based on stakeholder input to improve care delivered to hernia patients.

WAG-F8(m1Ycb) rats harboring a factor VIII gene mutation provide a new animal model for hemophilia A.

BACKGROUND: We recently described an inherited coagulopathy arising in an inbred colony of WAG/RijYcb rats. The bleeding phenotype, demonstrated by both male and female rats, included periarticular hemorrhage, spontaneous bruising, prolonged bleeding from minor wounds and maternal peripartum deaths. Coagulation testing of affected rats revealed normal prothrombin time but prolongation of activated partial thromboplastin time to twice that of controls. OBJECTIVE: To determine the specific coagulation factor and the underlying genetic defect responsible for the inherited coagulopathy in the WAG/RijYcb rats. RESULTS: Evaluation of individual clotting factor activities revealed that the affected animals had a specific deficiency of factor (F) VIII (FVIII). The FVIII gene (F8) has an autosomal location on chromosome 18 in rats, in contrast to its location on the X chromosome in mice and humans. Sequencing of F8 cDNA led to the identification of a point mutation resulting in a substitution, Leu176Pro, in the A1 domain, that is predicted to disrupt the tertiary structure of the FVIII molecule. Administration of human plasma or human recombinant FVIII corrects the coagulation abnormality in the affected animals. CONCLUSIONS: We have now identified the genetic basis of the hemostatic defect in the WAG/RijYcb rat colony. The larger size of rats relative to mice and the presence of this coagulation defect in both sexes provide a unique model, well-suited to the development of novel therapies for acquired and hereditary FVIII deficiencies.

Sigmoid colonic fistula secondary to Perfix-plug, left inguinal hernia repair.

The "plug and patch" mesh herniorrhaphy has become a popular option for inguinal hernia repair. Previous reports have documented several complications with some regularity. This case presents an additional complication and offers suggestions as to why this complication and others might occur.

Tolerability and anti-inflammatory effects of glucuronoxylomannan in collagen-induced arthritis.

This investigation was planned to assess the therapeutic efficacy of glucuronoxylomannan (GXM) in collagen-induced arthritis (CIA). GXM was isolated from culture filtrate of Cryptococcus neoformans var. gattii, serotype C. CIA was induced by the immunization of Dark Agouti rats with bovine type II collagen in incomplete Freund's adjuvant. GXM solution at two doses, 25 and 50 mg/kg, was administered intraperitoneally. Onset of i.p. injections of GXM to prevention and treatment groups was days 0 and 10 postimmunization, respectively. The WEHI-164 cell line was used for assaying tolerability, matrix metalloproteinase type 2 (MMP-2) activity and apoptosis. MMP-2 activity was assessed using zymography. For assessment of apoptosis, the terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labelling method was used. The results of this experiment showed that the treatment of CIA with GXM at a dose of 50 mg/kg could suppress disease development both prophylactically and therapeutically. This beneficial effect of GXM was associated with a significant decrease in the anti-CII antibody response compared with untreated rats. Moreover, GXM therapy could diminish MMP-2 activity, but it had no notable effect on apoptosis. GXM also showed a high tolerability compared with certain steroidal and non-steroidal anti-inflammatory drugs. We conclude that GXM suppresses the development of disease in CIA and it could be recommended as a new immunosuppressive and anti-inflammatory agent for further investigations.

Use of the prolene hernia system for inguinal hernia repair: retrospective, comparative time analysis versus other inguinal hernia repair systems.

No data are available for the duration of surgery for the various procedures currently used in hernia repair. This retrospective study was undertaken to determine the time required for the surgical repair of unilateral primary inguinal hernias using currently available procedures and to show specifically that the duration of surgery using the PROLENE Hernia System (PHS) was equal to or less than the duration of surgery using a plug-and-patch device. Data were collected from 1032 sequential hernia procedures performed by 16 surgeons at a community hospital between 1997 and 1999. To gain more accurate information to compare the PHS and plug-and-patch procedures data from four surgeons who had performed at least five of each procedure were used as the primary analysis database. The two most frequently used devices were the PHS (35.9%) and plug and patch (41.0%). The average times of surgery for these procedures were not significantly different (25.4 vs 27.2 minutes, respectively; P = 0.236). A significant variability was observed between surgeons in the duration of surgery and there was evidence for an inverse relationship between the duration of surgery and the number of procedures a surgeon had performed. Both procedures take approximately the same time to perform.

The Cryptococcus neoformans gene DHA1 encodes an antigen that elicits a delayed-type hypersensitivity reaction in immune mice.

When mice are vaccinated with a culture filtrate from Cryptococcus neoformans (CneF), they mount a protective cell-mediated immune response as detected by dermal delayed-type hypersensitivity (DTH) to CneF. We have identified a gene (DHA1) whose product accounts at least in part for the DTH reactivity. Using an acapsular mutant (Cap-67) of C. neoformans strain B3501, we prepared a culture filtrate (CneF-Cap67) similar to that used for preparing the commonly used skin test antigen made with C. neoformans 184A (CneF-184A). CneF-Cap67 elicited DTH in mice immunized with CneF-184A. Deglycosylation of CneF-Cap67 did not diminish its DTH activity. Furthermore, size separation by either chromatography or differential centrifugation identified the major DTH activity of CneF-Cap67 to be present in fractions that contained proteins of approximately 19 to 20 kDa. Using N-terminal and internal amino acid sequences derived from the 20-kDa band, oligonucleotide primers were designed, two of which produced a 776-bp amplimer by reverse transcription-PCR (RT-PCR) using RNA from Cap-67 to prepare cDNA for the template. The amplimer was used as a probe to isolate clones containing the full-length DHA1 gene from a phage genomic library prepared from strain B3501. The full-length cDNA was obtained by 5' rapid amplification of cDNA ends and RT-PCR. Analysis of DHA1 revealed a similarity between the deduced open reading frame and that of a developmentally regulated gene from Lentinus edodes (shiitake mushroom) associated with fruiting-body formation. Also, the gene product contained several amino acid sequences identical to those determined biochemically from the purified 20-kDa peptide encoded by DHA1. Recombinant DHA1 protein expressed in Escherichia coli was shown to elicit DTH reactions similar to those elicited by CneF-Cap67 in mice immunized against C. neoformans. Thus, DHA1 is the first gene to be cloned from C. neoformans whose product has been shown to possess immunologic activity.

CTLA-4 down-regulates the protective anticryptococcal cell-mediated immune response.

Cell-mediated immune (CMI) responses defined by delayed-type hypersensitivity (DTH) reactivity to cryptococcal culture filtrate antigen (CneF) can be either protective or nonprotective against an infection with Cryptococcus neoformans. The protective and nonprotective anticryptococcal DTH responses are induced by different immunogens and have differing activated-T-cell profiles. This study examined the effects of blockade of the interaction between cytotoxic T lymphocyte antigen 4 (CTLA-4) and its ligands B7-1 (CD80) and B7-2 (CD86) on the anticryptococcal DTH responses and protection. We found that CTLA-4 blockade at the time of immunization with the immunogen that induces the protective response, CneF, in complete Freund's adjuvant (CFA) or the immunogen that induces the nonprotective response, heat-killed cryptococcal cells (HKC), enhanced anticryptococcal DTH reactivity. In contrast, blocking CTLA-4 after the immune response was induced failed to enhance responses. Blockade of CTLA-4 in an infection model resulted in earlier development of the anticryptococcal CMI response than in control mice. Concomitant with increases in DTH reactivity in mice treated with anti-CTLA-4 Fab fragments at the time of immunization, there were decreases in cryptococcal CFU in lungs, spleens, and brains compared to controls. Blockade of CTLA-4 resulted in long-term protection, as measured by significantly increased survival times, only in mice given the protective immunogen, CneF-CFA. Anti-CTLA-4 treatment did not shift the response induced by the nonprotective immunogen, HKC, to a long-term protective one. Our data indicate that blockade of CTLA-4 interactions with its ligands may be useful in enhancing host defenses against C. neoformans.

Dendritic cells in the induction of protective and nonprotective anticryptococcal cell-mediated immune responses.

Dendritic cells (DC) can be divided into three subsets, Langerhans cells, myeloid DC (MDC), and lymphoid DC (LDC), based upon phenotypic and functional differences. We hypothesized that different DC subsets are associated with the development of protective vs nonprotective cell-mediated immune (CMI) responses against the fungal pathogen, Cryptococcus neoformans. To test this, mice were immunized with protective and/or nonprotective immunogens, and DC subsets in draining lymph nodes were assessed by flow cytometry. The protective immunogen (cryptococcal culture filtrate Ag-CFA), in contrast to the nonprotective immunogen (heat-killed cryptococci-CFA), the nonprotective immunogen mixed with the protective immunogen (cryptococcal culture filtrate Ag + heat-killed cryptococci-CFA), or controls, stimulated significant increases in total leukocytes, Langerhans cells, MDC, LDC, and activated CD4+ T cells in draining lymph nodes. The protective immune response resulted in significantly increased levels of anticryptococcal delayed-type hypersensitivity reactivity and activated CD4+ T cells at the delayed-type hypersensitivity reaction site. Draining lymph node LDC:MDC ratios induced by the protective immunogen were significantly lower than the ratios induced by either immunization in which the nonprotective immunogen was present. In contrast, mice given the nonprotective immunogen had LDC:MDC ratios similar to those of naive mice. Our data indicate that lymph node Langerhans cells and MDC are APC needed for induction of the protective response. The predominance of LDC in mice undergoing nonprotective responses suggests that lymph node LDC, like splenic LDC, are negative regulators of CMI responses. In addition to showing DC subsets associated with functional differences, our data suggest that the LDC:MDC balance, which can be modulated by the Ag, determines whether protective or nonprotective anticryptococcal CMI responses develop.

The third transmembrane helix of the cannabinoid receptor plays a role in the selectivity of aminoalkylindoles for CB2, peripheral cannabinoid receptor.

Two subtypes of the human cannabinoid receptor have been identified. The CB1 receptor is primarily distributed in the central nervous system, whereas the CB2 receptor is associated with peripheral tissue, including the spleen. These two subtypes are also distinguished by their ligand-binding profiles. The goal of this study was to identify critical residues in transmembrane region III (TM3) of the receptors that contribute to subtype specificity in ligand binding. For this purpose, a chimeric cannabinoid receptor [CB1/2(TM3)] was generated in which the TM3 of CB1 was replaced with the corresponding region of CB2. These receptors were stably expressed in Chinese hamster ovary cells for evaluation. The binding affinities of CB1/2(TM3) and the wild-type CB1 receptor to several prototype ligands were similar with one notable exception: the chimeric receptor exhibited a 4-fold enhancement in binding affinity to WIN 55,212-2 (K(d) = 4.8 nM) relative to that observed with CB1 (K(d) = 21.7 nM). Two additional aminoalkylindoles, JWH 015 and JWH 018, also bound the chimeric receptor (K(i) = 1.0 microM and 1.4 nM, respectively) with higher affinity compared with the wild-type CB1 (K(i) = 5.2 microM and 9.8 nM, respectively). Furthermore, the increase in binding affinities of the aminoalkylindoles were reflected in the EC(50) values for the ligand-induced inhibition of intracellular cAMP levels mediated by the chimeric receptor. This pattern mirrors the selectivity of WIN 55,212-2 binding to CB2 compared with CB1. Site-specific mutagenesis of the most notable amino acid changes in the chimeric receptor, Gly195 to Ser and Ala198 to Met, revealed that the enhancement in WIN 55,212-2 binding is contributed to by the Ser but not by the Met residue. The data indicate that the amino acid differences in TM3 between CB1 and CB2 play a critical role in subtype selectivity for this class of compounds.

Cutting edge: Role of C-C chemokine receptor 5 in organ-specific and innate immunity to Cryptococcus neoformans.

After intratracheal inoculation of the AIDS-associated pathogen Cryptococcus neoformans, 12-wk survival was >90% for CCR5+/+ mice but <25% for CCR5-/- mice. There were no defects in lung leukocyte recruitment (wk 5), pulmonary clearance, or delayed-type hypersensitivity in CCR5-/- mice. However, CCR5-/- mice had defects in leukocyte recruitment into the brain and, strikingly, in elimination of cryptococcal polysaccharide from the brain. In nonimmune CCR5-/- mice, there was a significant defect in macrophage recruitment after challenge with shed cryptococcal products (C. neoformans filtrate Ag) but not other nonspecific stimuli. Thus, CCR5 plays specific roles in innate immunity and organ-specific leukocyte trafficking during host defense against C. neoformans.

Differential regulation of immune responses by highly and weakly virulent Cryptococcus neoformans isolates.

Early inflammatory responses, delayed-type hypersensitivity (DTH) responses, and cytokine profiles were studied in mice infected by the pulmonary route with either a highly virulent isolate (NU-2) or a weakly virulent isolate (184A) of Cryptococcus neoformans. After infection, NU-2 remained in the lungs and the capsule became more pronounced during the first 24 h, whereas 184A induced an immediate inflammatory reaction and was rapidly cleared from the lungs. Cryptococcal antigen (GXM) appeared in sera early after infection with NU-2 and increased over the entire observation period. There was no detectable GXM in sera from 184A-infected mice. Both C. neoformans isolates induced anticryptococcal cell-mediated immune responses, but the responses had different profiles. DTH in NU-2-infected mice appeared at day 15 after infection and waned by day 21, whereas DTH in 184A-infected mice was present by day 5 and continued to increase. T helper 1 (Th1) cytokines (interleukin 2 [IL-2] and gamma interferon) were made by spleen cells early after infection with either isolate. NU-2-infected mice lost their ability to produce these cytokines, but 184A-infected mice retained it. IL-4, a Th2 cytokine, was not detected in infected mice. The regulatory cytokine IL-10 was made by spleen cells early but not later after infection with the highly virulent isolate and was not produced by spleen cells from 184A-infected mice. IL-10-deficient mice survived an NU-2 infection significantly longer than wild-type mice, suggesting that IL-10 is important in down-regulating the protective immune response. The induction of anergy appears to be responsible for the inability of NU-2-infected mice to control a C. neoformans infection.

Role of the C-C chemokine, TCA3, in the protective anticryptococcal cell-mediated immune response.

Activated T lymphocytes play a crucial role in orchestrating cellular infiltration during a cell-mediated immune (CMI) reaction. TCA3, a C-C chemokine, is produced by Ag-activated T cells and is chemotactic for neutrophils and macrophages, two cell types in a murine CMI reaction. Using a gelatin sponge model for delayed-type hypersensitivity (DTH), we show that TCA3 is a component of the expression phase of an anticryptococcal CMI response in mice. TCA3 mRNA levels are augmented in anticryptococcal DTH reactions at the same time peak influxes of neutrophils and lymphocytes are observed. Neutralization of TCA3 in immunized mice results in reduced numbers of neutrophils and lymphocytes at DTH reaction sites. However, when rTCA3 is injected into sponges in naive mice, only neutrophils are attracted into the sponges, indicating TCA3 is chemotactic for neutrophils, but not lymphocytes. We show that TCA3 is indirectly attracting lymphocytes into DTH-reactive sponges by affecting at least one other chemokine that is chemotactic for lymphocytes. Of the two lymphocyte-attracting chemokines assessed, monocyte-chemotactic protein-1 and macrophage-inflammatory protein-1alpha (MIP-1alpha), only MIP-1alpha was reduced when TCA3 was neutralized, indicating that TCA3 affects the levels of MIP-1alpha, which attracts lymphocytes into the sponges. TCA3 also plays a role in protection against Cryptococcus neoformans in the lungs and brains of infected mice, as evidenced by the fact that neutralization of TCA3 results in increased C. neoformans CFU in those two organs.

Immunological down-regulation of host defenses in fungal infections.

Fungal pathogens use multiple virulence factors to cause progressive disease. A mechanism that could be regarded as a virulence factor is the fungal pathogen's ability to evade or down-regulate host protective mechanisms. Cryptococcus neoformans is an excellent example of a fungal pathogen that can down-regulate both innate and immune host protective mechanisms. Cr. neoformans is a basidiomycetous yeast-like organism that causes cryptococcosis, a frequently fatal disease in man. This organism produces a capsule that inhibits phagocytosis, and the excess capsular material sloughs off and gets into the bloodstream where it causes L-selectin to shed from the leukocyte surface resulting in reduced migration of leukocytes into the site of infection. Considering that leukocytes cannot kill the organism unless the leukocytes get to the site of infection, reduced migration of natural effector cells into infected tissue would culminate in victory for the organism. Intravascular capsular polysaccharides of Cr. neoformans also induce regulatory T cells that inhibit the protective cell-mediated immune response. Isolates of Cr. neoformans that produce excessive capsular material in the host are highly virulent and a major contribution to their virulence is the ability of the capsular polysaccharide to down-modulate both innate and immune host defensive measures.

Mechanisms for induction of L-selectin loss from T lymphocytes by a cryptococcal polysaccharide, glucuronoxylomannan.

Disseminated cryptococcosis is accompanied by cryptococcal polysaccharides in the serum and the lack of cellular infiltrates in infected tissues. Cryptococcal polysaccharides given intravenously to mice inhibit the influx of T lymphocytes into the sites of cell-mediated immune response. The focus here was to determine whether cryptococcal polysaccharides modulate the expression of molecules, such as L-selectin, that are important in extravasation of T cells. Cryptococcal glucuronoxylomannan (GXM), but not galactoxylomannan or mannoprotein, was found to cause loss of L-selectin from freshly isolated human T cells of both CD4 and CD8 subsets and from Jurkat cells. With the signaling-pathway inhibitors staurosporine (which inhibits protein kinase C) and herbimycin A (which inhibits protein tyrosine kinases), we showed that GXM or the cryptococcal culture filtrate antigen CneF directly induces L-selectin loss from CD4(+) and CD8(+) T cells via a herbimycin A-sensitive pathway(s) presumably involving one or more protein tyrosine kinases but not via a pathway involving protein kinase C. Loss of L-selectin from the T cells before the T cells have a chance to bind to L-selectin ligands on endothelial cells would be expected to prevent T-cell migration into inflamed tissues and/or lymph organs.

Pathogenesis of Cryptococcus neoformans is associated with quantitative differences in multiple virulence factors.

Two isolates of Cryptococcus neoformans were previously described as being highly divergent in their level of capsule synthesis in vivo and in their virulence for mice. The highly virulent isolate (NU-2) produced more capsule than a weakly virulent isolate (184A) in vitro under tissue culture conditions and in vivo. This investigation was done to determine if there were differences between the two isolates in other factors that might also contribute to virulence. Growth rate was not a factor as NU-2 grew more slowly than 184A. Based on PCR fingerprinting the two isolates were genetically different providing an opportunity to examine differences in multiple virulence traits. Quantitative analysis revealed that NU-2 expressed significantly more melanin and mannitol than did 184A. Although the isolates expressed the same capsular chemotype, NU-2 produced an additional structure reporter group (SRG) under tissue culture conditions that was not present when grown in glucose salts/urea/basal medium (GSU). Capsular polysaccharide SRGs of 184A were unaffected by shifting the growth conditions from GSU to tissue culture conditions. Our results suggest that pathogenesis of a C. neoformans strain is dictated by the quantitative expression of the strain's combined virulence traits. Regulators of the expression of these genes may be playing key roles in virulence.

Liposomes, a potential immunoadjuvant and carrier for a cryptococcal vaccine.

Mice immunized with a cryptococcal culture filtrate antigen (CneF) emulsified in complete Freund's adjuvant (CFA) develop an anticryptococcal cell-mediated immune response (CMI). CMI is detected by delayed-type hypersensitivity (DTH) reactions and by enhanced clearance of Cryptococcus neoformans from infected tissues. The objective of this research was to evaluate anticryptococcal DTH reactivity and clearance of cryptococci from groups of mice immunized with CneF encapsulated into liposomes (CneF-liposome) and compare the results to results from mice immunized with CneF-CFA. CBA/J mice were injected subcutaneously with vaccines or control formulations (saline-liposome or saline-CFA). Six days later the mice were footpad tested to assess their DTH response to CneF or the animals were challenged intravenously with 10(5) viable C. neoformans to determine clearance of infection. Clearance was evaluated 7 days later by enumeration of cryptococcal colony forming units (CFU) in lungs, spleens, livers, and brains of the infected mice. The CneF-liposome formulation induced a positive anticryptococcal DTH response and elicited increased clearance of C. neoformans from tissues as compared to mice treated with saline-liposome. Even though the CneF-liposome preparation did not induce as strong of a DTH response or as much protection as did CneF-CFA, our results indicate that liposomes are promising carriers for immunization with cryptococcal antigen and that such immunization can provide some protection to subsequent infection with C. neoformans.

Antigen-induced protective and nonprotective cell-mediated immune components against Cryptococcus neoformans.

Mice immunized with two different cryptococcal antigen preparations, one a soluble culture filtrate antigen (CneF) in complete Freund's adjuvant (CFA) and the other heat-killed Cryptococcus neoformans cells (HKC), develop two different profiles of activated T cells. CneF-CFA induces CD4+ T cells responsible for delayed-type hypersensitivity (DTH) reactivity and for amplification of the anticryptococcal DTH response, whereas HKC induce CD4+ and CD8+ T cells involved in anticryptococcal DTH reactivity and activated T cells which directly kill C. neoformans cells. The main purpose of this study was to assess the level of protection afforded by each of the two different T-cell profiles against challenge with viable C. neoformans cells, thereby identifying which activated T-cell profile provides better protection. CBA/J mice immunized with CneF-CFA had significantly better protective responses, based on better clearance of C. neoformans from tissues, on longer survival times, and on fewer and smaller lesions in the brain, than HKC-immunized mice or control mice similarly infected with C. neoformans. Both immunization protocols induced an anticryptococcal DTH response, but neither induced serum antibodies to glucuronoxylmannan, so the protection observed in the CneF-CFA immunized mice was due to the activated T-cell profile induced by that protocol. HKC-immunized mice, which displayed no greater protection than controls, did not have the amplifier cells. Based on our findings, we propose that the protective anticryptococcal T cells are the CD4+ T cells which have been shown to be responsible for DTH reactivity and/or the CD4+ T cells which amplify the DTH response and which have been previously shown to produce high levels of gamma interferon and interleukin 2. Our results imply that there are protective and nonprotective cell-mediated immune responses and highlight the complexity of the immune response to C. neoformans antigens.

What makes Cryptococcus neoformans a pathogen?

Life-threatening infections caused by the encapsulated fungal pathogen Cryptococcus neoformans have been increasing steadily over the past 10 years because of the onset of AIDS and the expanded use of immunosuppressive drugs. Intricate host-organism interactions make the full understanding of pathogenicity and virulence of C. neoformans difficult. We discuss the current knowledge of the characteristics C. neoformans must possess to enter the host and establish progressive disease: basic growth requirements and virulence factors, such as the polysaccharide capsule; shed products of the organism; melanin production; mannitol secretion; superoxide dismutase; proteases; and phospholipases.

Antibody and/or cell-mediated immunity, protective mechanisms in fungal disease: an ongoing dilemma or an unnecessary dispute?

Historically there has been controversy on the relative importance of antibody- and cell-mediated immune responses in the protection against fungal pathogens. The controversy was fuelled by the difficulties encountered in obtaining consistent results with polyclonal antibody experiments and I inducing long-lasting immune protection by vaccinations with induce stron cell-mediated responses. Recent studies indicate that both antibody- and cell-mediated immune responses can contribute to host protection against Candida albicans and C. neoformans. At the present time the major issue is not the relative importance of antibody- and cell-mediated immune responses but rather, the mechanisms by which the two arms of the immune system function and cooperate.