A Biomechanical Analysis of Tibial Fixation Methods in Hamstring-Graft Anterior Cruciate Ligament Reconstruction

BACKGROUND

There are conflicting results on the biomechanical properties of tibial fixation devices in anterior cruciate ligament reconstruction. The objective of this study is to compare the initial biomechanical properties of tibial fixation in hamstring-graft ACL reconstruction with interference screw, suspension button, and Tape Locking Screw^TM devices. We hypothesized there are no differences in the initial biomechanical properties of these three tibial fixation techniques.

METHODS

Twenty-one fresh-frozen porcine tibiae were equally divided into three groups of seven tibiae to evaluate the fixation of human hamstring tendon grafts with interference screw, suspension button, or Tape Locking Screw fixation. Using a servohydraulic materials testing system, each graft was subjected to 500 cycles of loading followed by a monotonic failure test.

RESULTS

Interference screw fixation demonstrated significantly lower cyclic displacement (1.28 ± 0.73 mm) than the other groups fixated with either a suspension button device (2.54 ± 0.27 mm, p = 0.003) or a Tape Locking Screw (2.32 ± 0.42 mm, p = .009), and a significantly greater cyclic stiffness (212.19 ± 40.30 N/mm) than the Tape Locking Screw (137.64 ± 26.17 N/mm, p = 0.002). The interference screw also demonstrated significantly higher pullout stiffness (166.83 ± 23.22 N/mm) than the suspension button (112.78 ± 24.14 N/mm, P = 0.002) and Tape Locking Screw (109.11 ± 12.91 N/mm, P = 0.0002).

CONCLUSIONS

Tibial fixation with an interference screw demonstrated superior biomechanical properties for cyclic testing compared to the suspension button and Tape Locking Screw. Load to failure did not differ between groups, and there were no significant biomechanical differences between the suspension button and Tape Locking Screw fixation devices.

CLINICAL RELEVANCE

Despite the initial biomechanical differences, all three fixation devices exhibited mean loads to failure and cyclic displacements below clinically relevant thresholds of failure. These data suggest all three fixation methods are viable options for achieving a functional ACL reconstruction.Level of Evidence: V.

Restoration of spinal alignment and disk mechanics following polyetheretherketone wafer kyphoplasty with StaXx FX

BACKGROUND AND PURPOSE

EPFs sustained during VCFs degrade the disk's ability to develop IDP under load. This inability to develop pressure in combination with residual kyphotic deformity increases the risk for adjacent vertebral fractures. We tested the hypothesis that StaXx FX reduces kyphosis and endplate deformity following vertebral compression fracture, restoring disk mechanics.

MATERIALS AND METHODS

Eight thoracolumbar, 5-vertebrae segments were tested. A void was selectively created in the middle vertebra. The specimens were compressed until EPF and to a grade I-II VCF. PEEK wafer kyphoplasty was then performed. The specimens were then tested in flexion-extension (±6 Nm) under 400-N preload intact, after EPF, VCF, and kyphoplasty. Endplate deformity, kyphosis, and IDP adjacent to the fractured body were measured.

RESULTS

Vertebral body height at the point of maximal endplate deformity decreased after EPF and VCF and was partially corrected after StaXx FX, remaining less than intact (P = .047). Anterior vertebral height decreased after VCF (P = .002) and was partially restored with StaXx FX, remaining less than intact (P = .015). Vertebral kyphosis increased after VCF (P < .001) and reduced after StaXx FX, remaining greater than intact (P = .03). EPF reduced IDP in the affected disk in compression-flexion loading (P < .001), which was restored after StaXx FX (P = 1.0). IDP in the unaffected disk did not change during testing (P > .3).

CONCLUSIONS

StaXx FX reduced endplate deformity and kyphosis, and significantly increased anterior height following VCF. Although height and kyphosis were not fully corrected, the disk's ability to pressurize under load was restored.

Primary and coupled motions after cervical total disc replacement using a compressible six-degree-of-freedom prosthesis

This study tested the hypotheses that (1) cervical total disc replacement with a compressible, six-degree-of-freedom prosthesis would allow restoration of physiologic range and quality of motion, and (2) the kinematic response would not be adversely affected by variability in prosthesis position in the sagittal plane. Twelve human cadaveric cervical spines were tested. Prostheses were implanted at C5-C6. Range of motion (ROM) was measured in flexion-extension, lateral bending, and axial rotation under ± 1.5 Nm moments. Motion coupling between axial rotation and lateral bending was calculated. Stiffness in the high flexibility zone was evaluated in all three testing modes, while the center of rotation (COR) was calculated using digital video fluoroscopic images in flexion-extension. Implantation in the middle position increased ROM in flexion-extension from 13.5 ± 2.3 to 15.7 ± 3.0° (p < 0.05), decreased axial rotation from 9.9 ± 1.7 to 8.3 ± 1.6° (p < 0.05), and decreased lateral bending from 8.0 ± 2.1 to 4.5 ± 1.1° (p < 0.05). Coupled lateral bending decreased from 0.62 ± 0.16 to 0.39 ± 0.15° for each degree of axial rotation (p < 0.05). Flexion-extension stiffness of the reconstructed segment with the prosthesis in the middle position did not deviate significantly from intact controls, whereas the lateral bending and axial rotation stiffness values were significantly larger than intact. Implanting the prosthesis in the posterior position as compared to the middle position did not significantly affect the ROM, motion coupling, or stiffness of the reconstructed segment; however, the COR location better approximated intact controls with the prosthesis midline located within ± 1 mm of the disc-space midline. Overall, the kinematic response after reconstruction with the compressible, six-degree-of-freedom prosthesis within ± 1 mm of the disc-space midline approximated the intact response in flexion-extension. Clinical studies are needed to understand and interpret the effects of limited restoration of lateral bending and axial rotation motions and motion coupling on clinical outcome.

Platelet-activating factor and the production of human interferon-gamma

Platelet-activating factor (PAF) was tested for its ability to alter yields of human interferon (IFN) produced from peripheral blood mononuclear cells (PBMC). Using different concentrations of phytohemagglutinin (PHA) we could not demonstrate a consistent effect of PAF at any concentration tested on the yield of IFN-gamma. Similarly, although PAF was associated with a slight enhancement of IFN-gamma yields when PBMC were induced by interleukin-2 (IL-2), the results were not statistically significant. No effect was observed on the accumulation of human IFN-gamma mRNA induced by PHA. Furthermore, PAF did not enhance yields of IFN-gamma when the cells were induced by poly I:poly C. We conclude that although PAF may have a role in sepsis, it is not likely that this is in any way related to its ability to significantly alter the yield of interferons.

Intraluminal antibiotic treatment of central venous catheter infections in patients receiving parenteral nutrition at home

We carried out an open, uncontrolled, prospective study to evaluate intraluminal antibiotic therapy for bloodstream infections arising from subcutaneously tunneled central venous catheters in patients receiving parenteral nutrition therapy at home. Seven bacterial infections were treated with intraluminal antibiotics (mean duration, 8.6 days) sometimes accompanied by systemic antibiotics (mean duration, 2.1 days). All seven infections were cured. Two infections caused by Candida species were treated with intraluminal amphotericin B. Fungal infections was suppressed during treatment but later relapsed, as confirmed by pulsed field DNA electrophoresis typing of bloodstream isolates. The concentration of antibiotic was assayed in intraluminal fluid from catheters of patients receiving treatment with vancomycin or gentamicin. The concentration was initially approximately 5 mg/mL, and it remained at > or = 2.5 mg/mL throughout the period that the solution was locked in the catheter. Our findings show that intraluminal therapy is effective against selected bacterial infections and can suppress fungal infections in subcutaneously tunneled catheters.

Hyperferritinemia in reactive hemophagocytic syndrome report of four adult cases

Four patients were diagnosed with reactive hemophagocytic syndrome (RHPS) during a 7 month period. Of these, three patients were diagnosed with acquired immunodeficiency syndrome complicated by disseminated Mycobacterium tuberculosis infection, incompletely treated Pneumocystis carinii pneumonia and disseminated histoplasmosis respectively. The fourth patient had non-Hodgkin's lymphoma of the mature T-cell phenotype. Fever, bicytopenia, or pancytopenia, elevated serum lactate dehydrogenase (LDH) level (> 1,000 IU/L), and hemophagocytic histiocytosis in smears of bone marrow aspirate were present in all patients. Hyperferritinemia (> 10,000 ng/ml) was present in all (range 34,976 to 425,984 ng/mL) and showed a decrease in the two patients who responded to therapy. Hyperferritinemia (> 10,000 ng/ml) and elevated serum LDH (> 1,000 IU/L) are important clues to the diagnosis of RHPS in the febrile cytopenic patient with immunodeficiency.

Induction, transcription, synthesis, and adsorption of interleukin-1 by dialyzer membranes

This study was designed to dissect the direct effect of dialyzer membrane on interleukin-1 (IL-1) induction from those of complement activation, mechanical stimulation, acetate/bicarbonate and endotoxin diffusion, and cell type interactions. To this end, a suspension of P388D1 murine macrophages in a complement-free culture medium containing 10% heat-inactivated serum, a closed-loop system consisting of tubing alone or with a hollow-fiber cuprammonium cellulose (CU) or polyacrylonitrile (PAN) dialyzer, and a roller pump were used. The dialysate compartment was filled with the same medium and capped. Cell suspension was recirculated at 300 mL/min for 3 h. Cells and supernates were separated, and adhering proteins were eluted. All samples tested negative for endotoxin. IL-1 mRNA was greatest with CU, followed by PAN and tubing alone. IL-1 in the supernate was greater with CU than with either tubing alone or PAN (P < 0.005; analysis of variance), which showed comparable values. IL-1 eluted from loops was greatest with PAN dialyzers, followed by sets with CU dialyzers and tubing alone (P < 0.001; analysis of variance). Thus, both CU and PAN membranes directly induce IL-1. However, avid adsorption by PAN attenuates the rise in circulating IL-1.

Enhanced yields of gamma interferon in prolactin treated human peripheral blood mononuclear cells

Prolactin is a peptide hormone with effects on a number of target organs including the immune system. It has been shown that animals rendered hypoprolactinemic have impaired delayed hypersensitivity, impaired macrophage activation and altered secretion of gamma interferon (IFN). Using peripheral blood mononuclear cells (PBMC) and inducing the cells to produce gamma IFN with a range of inducers, we have studied the effects of a number of hormones on IFN production. Using cells from normal donors, we have found that prolactin in concentrations of 10(-8) M or greater, can significantly enhance the production of gamma IFN. The effect was dose related and was observed when lectins (PHA and Con A), but not anti CD3 antibodies, ionophones, or IL-2 were used to induce the cells. The presence of prolactin in concentrations above that encountered in the fetal bovine serum used to incubate the cells resulted in a doubling or more of the IFN produced. The tests were performed on 30 occasions with cells drawn from 21 individuals. On all but three occasions, yield enhancement was observed in the presence of prolactin. The mechanism of the effect was investigated, and genistein, a tyrosine kinase inhibitor, was found to abort the influence of prolactin on gamma IFN production. These studies indicate prolactin in physiological concentrations can enhance the production of gamma IFN from cells from normal donors.

The effect of gonadotropins on the production of human interferon-gamma by mononuclear cells

Gonadotropins--follicle-stimulating hormone (FSH), luteinizing hormone (LH), and human chorionic gonadotropin (HCG)--and the related agent thyrotropin were shown to enhance yields of interferon-gamma (IFN-gamma) from human peripheral blood mononuclear cells (PBMC) significantly when calcium ionophores (ionomycin or A23187) were used as inducers. The enhancement increased the IFN yields four- to eight-fold. Induction with other inducers, (such as lectins, interleukin-2 (IL-2), and anti CD3, was not associated with enhancement of the IFN yields by gonadotropins. Concentrations of gonadotropins associated with pregnancy (HCG) or menopause (FSH and LH) were able to enhance IFN-gamma yields. Addition of the gonadotropins to the cells after the ionophore gave the greatest degree of enhancement. Perturbation of the calcium messenger system or nonspecific stimulation of adenyl cyclase failed to influence the IFN yield enhancing effect of the gonadotropins. No effect of gonadotropins was observed on IFN bioactivity.

The paradoxical effects of somatostatin on the bioactivity and production of cytotoxins derived from human peripheral blood mononuclear cells

Somatostatin (SMS), a naturally occurring peptide is known to inhibit the production of certain protein molecules and to diminish the ability of peripheral blood mononuclear cells to proliferate. We tested the effects of three forms of SMS on the bioactivity of both lymphotoxin (LT) and tumour necrosis factor (TNF). We also tested the effects of these agents on production of cytotoxins by peripheral blood mononuclear cells. We found the 28 amino acid form of SMS significantly enhanced the bioactivity of both LT and TNF (10(-9) M concentration) when tested in mouse L cells. The 14 amino acid form of SMS enhanced LT (10(-9) M concentration) activity but not TNF activity. The first 14 amino acid form of SMS-28 (amino terminal) did not affect bioactivity of the cytotoxin. In contrast, the naturally occurring 14 amino acid form of SMS (10(-8) M concentration) significantly diminished production of cytotoxin by human peripheral blood mononuclear cells. Cytotoxin produced by the latter was shown to be a combination of both LT and TNF. Similarly after SMS exposure, the cytotoxin produced remained a mixture of LT and TNF in roughly similar proportions. It thus appears that certain forms of SMS can enhance the bioactivity of cytotoxins, but at the same time decrease the production of these cytotoxins.

The effect of somatostatin on the production of human interferons by mononuclear cells

Somatostatin (SMS) is a tetradecapeptide which can inhibit the secretion of a number of peptides produced by the endocrine or nervous systems. SMS 201-995 (octreotide) is a somatostatin analogue with very potent somatostatin activities. We have been investigating the effects of both SMS and octreotide on the production of human interferon (IFN). We obtained human peripheral blood mononuclear cells from normal donors and induced them to produce IFN in the presence or absence of a number of peptides possessing somatostatin activities. SMS and octreotide were shown to inhibit the secretion of INF-gamma but not IFN-alpha. Concentrations of 10(-6) M were shown to decrease yields when Concanavalin A or phytohemagglutin were used as the inducer. Higher concentrations had a progressively greater effect. No effects were observed on IFN-gamma production if interleukin 2, ionomycin, or various natural antigens were used to induce the cells. The 28-amino acid form of somatostatin had some effects on gamma IFN yields but the first 14-amino acid fragment of this peptide moiety did not. No effect of any of these compounds was observed on IFN bioactivity. These studies indicate SMS may have some regulatory action on the secretion of immunomodulators in vitro but the concentrations required are well above those encountered under physiologic circumstances, suggesting SMS may not play an important regulatory role governing such secretion in vivo.

The effect of vitamin D3 on the production of cytotoxic factors by human peripheral blood mononuclear cells

Vitamin D3 at a concentration of 300 nM was shown to significantly reduce the yields of cytotoxin produced by human peripheral blood mononuclear cells. Reduction of cytotoxin titers occurred when induction was performed with either concanavalin A, interleukin 2, or ionomycin. Typing of this cytotoxin was accomplished using antisera that were prepared by immunization of rabbits with either recombinant tumor necrosis factor or lymphotoxin. Both antisera were demonstrated to neutralize the cytotoxic activity produced by the peripheral blood mononuclear cells in the presence or absence of vitamin D3. These latter experiments suggested that the cytotoxin in question might be lymphotoxin. Vitamin D3 was also shown to decrease cytotoxin production by a transformed B-cell line known to produce only lymphotoxin, supporting the concept that this vitamin could diminish yields of lymphotoxin at least under certain circumstances. However, purified adherent cells induced by Escherichia coli lipopolysaccharide produced a cytotoxin that was also inhibited by the presence of vitamin D3. Indomethacin failed to influence the effects of vitamin D3 on the production of the cytotoxin. These studies suggest that vitamin D3 may have a role in regulating the secretion of cytotoxic factors which may be important in the defense against neoplastic diseases.

The regulation of interferon production by aspirin, other inhibitors of the cyclooxygenase pathway and agents influencing calcium channel flux

Interferon is a family of potent antiviral agents which can activate macrophages, enhance cell surface markers, or influence antibody production. Three major types of human interferon are known to exist and have been designated interferons alpha, beta, and gamma. Because of its unique antiviral properties and its ability to influence the immune response, interferon has long been considered a potential therapeutic intervention in the treatment of infections and possibly neoplastic diseases. Two potential means to utilize interferon might be considered: One method would involve the administration of exogenous interferon, but an alternative might augment natural interferon production. We have been investigating a series of pharmacological agents that might influence its production and action. Since prostaglandins influence the immune response, we have investigated the effect of these cyclic fatty acids and those agents that influence their production on soluble protein mediators of the immune response on interferon. Our studies have focused on the effects of acetylsalicylic acid on the interferon system. We have demonstrated that prostaglandins of the E series can significantly reduce the yields of human interferon gamma, but not alpha (the two species of leukocyte derived interferon). In general, yields of gamma interferon produced by peripheral blood mononuclear cells in the presence of PGE2 (0.1 to 0.01 ugm/ml) were approximately 15% of those produced in the absence of these substances. In contrast, when acetylsalicylic acid (10 ugm/ml) was added to the cultures of peripheral blood mononuclear cells yields of gamma interferon increased more than threefold. When examining the effects of acetylsalicylic acid on human alpha interferon production, we were also to enhance interferon harvests although we could not demonstrate an adverse effect of prostaglandins on the production of these bioactive proteins. Addition of acetylsalicylic acid and prostaglandins simultaneously to our cultures had a negative effect on gamma interferon production, but still was associated with enhanced yields of interferon alpha. In examining how prostaglandins might influence interferon production, we began to study other cellular requirements for lymphokine production including those processes which were calcium dependent. Preliminary studies demonstrated that production of human interferon gamma by peripheral blood mononuclear cells was calcium dependent, but production of human interferon alpha was not. Thus, almost all agents studied that influenced calcium dependent intracellular processes influenced the titer of human interferon gamma produced, but not that of human interferon alpha. In examining this phenomenon more closely we noted the calcium channel flux was critical to the production of interferon gamma, hence agents enhancing channel flux(Bay K 8644) increased the production of human interferon gamma, but agents diminishing channel flux (specifically) channel blockers diminished production of this interferon species. These effects depended on the nature of the specific inducing agent. We are now examining the relationship of our observations with calcium to our earlier work with acetylsalicylic acid.

Calcium and the production of interferon by human peripheral blood mononuclear cells

We have studied the ability of human peripheral blood mononuclear cells (PBMC) to produce interferon-alpha (IFN-alpha) and IFN-gamma in the presence of pharmacologic agents known to influence calcium transport or calcium-dependent processes. We have found that the production of human (Hu) IFN-gamma is affected significantly by alterations in calcium flux; however, this influence is dependent upon the nature of the compound used to induce IFN. Inhibitors of protein kinase C decreased yields of IFN-gamma but inhibition of calmodulin did not. The presence of vitamin D3 reduced IFN-gamma titers when PHA and IL-2 were used to induce IFN, but not when ionomycin was used as the inducer. The production of IFN-gamma by PBMC was reduced by diminished concentrations in extracellular calcium but not extracellular magnesium. In contrast, neither the presence of any of the pharmacological agents tested above nor the reduction of the calcium concentration influenced the production of HuIFN-alpha by PBMC.

The effect of beta-estradiol, progesterone and testosterone on the production of human leukocyte derived interferons

Sex hormones including estrogens, progesterone and testosterones are known to have adverse effects on the immune system and particularly on the proliferative response. Since cytokine production is known to be dissociable from the proliferation of lymphocytes and since other steroid hormones profoundly affect cytokine production, we felt it would be important to know the effect of sex steroids on the production of interferons (IFN), particularly since the latter are known to be key substances in the immune response. We have shown estradiol can slightly reduce gamma IFN yields with certain inducers (Con A, SEA) but only in pharmacologic concentrations. Similarly, progesterone had a modest effect in the same concentrations but only when Con A was the inducer. Testosterone did not effect IFN titers at any concentration. None of the sex steroids affected alpha IFN production and none of them influenced the bioactivity of either IFN species. In all cases these hormones diminished proliferative responses as has been previously noted.

Reversal of the effects of cyclosporin A on the production of human interferon-gamma

Previous reports have documented that cyclosporin A (CsA) can inhibit the production of interferon-gamma (HuIFN-gamma) and interleukin-2 (IL-2). In this report we have extended these earlier findings and have demonstrated that the defect in the production of HuIFN-gamma persists even after the CsA is removed and is associated with altered synthesis of other lymphokines, mainly a cytotoxin and leukocyte migration inhibition factor. In the presence of recombinant exogenous IL-2, the effect of CsA on the synthesis of HuIFN-gamma can be reversed depending on the concentrations of both the IL-2 and CsA. In addition, the presence of the calcium ionophore A23187 partially reverses the inhibitory effect of CsA by synergistically enhancing the synthesis of HuIFN-gamma.

Optimal conditions for the induction of human mononuclear leukocytes by complexed polyinosinic-polycytidylic acid

We have defined the optimal circumstances for the induction of human interferon alpha (Hu IFN alpha) in peripheral blood mononuclear cells (PBMC) using complexed polyinosinic-polycytidylic acids (poly rIrC). We have found that a poly rIrC concentration of only 0.1 microgram m/ml or 100 fold less than commonly used in fibroblasts produced maximal yields. Similarly, we have found that the optimal concentration of DEAE-D was 250 micrograms m/ml. Only a minimum exposure period of 30 minutes to the poly rIrC-DEAE-D mixture was found necessary, but the temperature of this incubation was not found to be a critical variant. Finally, we found that addition of exogenous calcium to the inducing solution failed to influence the ultimate titers of the IFN produced.

Evaluation of the in vitro production of interferon gamma and other lymphokines in uremic patients

It has been suggested that a deficient immune response can be responsible at least partially for the high risk of infections and neoplasia in uremic patients. Since interferon (IFN) is critical to the immune response, we have evaluated the in vitro production of IFN-gamma and other lymphokines by peripheral blood mononuclear cells (PBMC) drawn from patients with end-stage renal disease and appropriate controls. We have correlated production of lymphokines by these cells with proliferative response to different mitogens. It was found that the secretion of IFN-gamma in response to all three mitogens was elevated in these patients compared with the control group. This elevation was significant with both phytohemagglutin and staphylococcal enterotoxin A, but not with Con A. No significant difference was observed in production of lymphotoxins, IL-2, and leukocyte migration inhibition responses. In contrast the proliferative response appeared diminished in the PBMC of uremic patients. We concluded that defective lymphokine generation is not a major immunological problem in patients with end-stage renal disease. Indeed, they appear to release excess amount of IFN-gamma which is known to be a macrophage-activating factor. It is suggested that high IFN-gamma activity could enhance the secretion of IL-1 or endogenous pyrogen and result in development of febrile reactions in dialysis patients.

Effect of acetyl salicylic acid on production and action of leukocyte-derived interferons

Although acetylsalicylic acid does not itself induce interferon, acetylsalicylic acid was found to significantly enhance the production of both human alpha interferon and human gamma interferon when added with the appropriate inducers to cultures of human peripheral blood mononuclear cells. The mechanisms associated with this effect were investigated.

The effect of corticosteroids and other antineoplastic agents on the generation of leukocyte migration inhibition factor

We have shown that hydrocortisone in physiological concentrations can inhibit the production of leukocyte migration inhibition factor (LMIF), but does not diminish the action of this lymphokine. Other agents tested failed to influence LMIF production. Inhibition of LMIF production by corticosteroids was influenced by the nature of the stimulus used for the production as an effect could be seen with PHA or Con A, but not Staphylococcal enterotoxin A (SEA). Production of LMIF was promptly restored after removal of the steroids. Furthermore, addition of a calcium ionophore to PHA restored the production of LMIF even in the presence of corticosteroids. In contrast, addition of exogenous IL-2 did not correct the defect in lymphokine secretion. We believe that inhibition of the production of LMIF by steroid may lead to defective granulocytic function and thus, predispose to infection.

The effect of hydrocortisone on the production of gamma-interferon and other lymphokines by human peripheral blood mononuclear cells

Concentrations of hydrocortisone as low as 0.08 microgram/ml significantly reduced the yields of gamma-interferon (IFN-gamma) when phytohemagglutinin (PHA) or concanavalin A (ConA) were used as inducers; however, when staphylococcal enterotoxin A was utilized, higher concentrations (5.0 micrograms/ml) were required to achieve the same effect. Yields of interleukin-2 (IL-2) and lymphotoxin were also found to be sensitive to the effects of the steroids, but expressions of TAC antigen was not generally affected by these agents. In contrast to the effects of steroids on cell proliferation, lymphokine production remained suppressed after steroid withdrawal. Hydrocortisone appeared to influence the concentrations of cyclic nucleotides following lectin stimulation, but attempts to correct these alterations or to add exogenous IL-2 failed to restore lymphokine production to normal levels. Addition of the calcium ionophore A23187 partially restored IFN-gamma production. We conclude that the effects of corticosteroids on the yields of lymphokines, including IFN-gamma, are profound. The depression of lymphokine production appears to be associated with a number of alterations in the cell, including depression of protein synthesis, alterations in cyclic nucleotides, and diminution of the production of cofactors necessary for IFN-gamma production. Enhancement of the flux of calcium into the cell may restore some of the ability to produce IFN-gamma.

Interferon responses in maternal and fetal mice

The kinetics of maternal-fetal interferon and a chemical interferon inducer were studied in Swiss-Webster white mice at 8, 15, and 19 days of gestation. Crude interferon was administered by maternal tail vein injection to one group. There was no transfer of interferon to the fetus despite high maternal levels. A chemical interferon inducer (10-carboxymethyl-9-acridanone) was given intramuscularly to a second group. Both maternal and fetal interferon responses rapidly reached significant levels, although the fetal response was less than that of the mother. Presence of the inducer was demonstrated in both maternal and fetal samples, indicating placental transport of the chemical to the fetus. The implications of these findings for the fetal immune response are discussed.