Lk Spencer

Cis‐UROCANIC ACID SYNERGIZES WITH HISTAMINE FOR INCREASED PGE2 PRODUCTION BY HUMAN KERATINOCYTES: LINK TO INDOMETHACIN‐INHIBITABLE UVB‐INDUCED IMMUNOSUPPRESSION

Abstract— There is considerable evidence that suppression of the immune system by UVB (280–320 nm UV) irradiation is initiated by UVB‐dependent isomerization of a specific skin photoreceptor, urocanic acid (UCA), from the trans to the cis form. Previous studies have confirmed that cis‐UCA administration to mice 3–5 days prior to hapten sensitization at a distant site, suppresses the contact hypersensitivity (CHS) response upon challenge. This study demonstrates in mice that cis‐UCA, like UVB, suppresses CHS to trinitrochlorobenzene by a mechanism partly dependent on prostanoid production. In vitro experimentation showed that human keratinocytes, isolated from neonatal foreskin, increased prostaglandin E2 (PGE2) production in response to histamine but not UCA alone. However, cis‐UCA synergized with histamine for increased PGE2 production by keratinocytes. cis‐urocanic acid also increased the sensitivity of keratinocytes for PGE2 production in response to histamine. Prostaglandin E2 from keratinocytes exposed to cis‐UCA and histamine may contribute directly, or indirectly, to the regulation of CHS responses by UVB irradiation.

Bacterial killing in vitro by abscess-derived neutrophils.

In the absence of antimicrobial therapy, bacteria such as Bacteriodes fragilis, Escherichia coli and Proteus mirabilis may persist within an intra-abdominal abscess in the presence of large numbers of neutrophils which, under optimal conditions in vitro, can readily phagocytose and kill the same bacterial strains. Neutrophils taken from abscesses induced by gram-negative bacteria such as those above contain viable organisms. On incubation in vitro in the presence of serum, these neutrophils kill the bacteria phagocytosed in the abscess poorly, if at all, yet can readily kill organisms added in vitro. To determine possible mechanisms that might explain this, we examined the bactericidal activity in vitro of neutrophils from a range of abscesses induced by one or two species of bacteria plus an abscess-potentiating agent, bran. The organisms studied were B. fragilis, E. coli, P. mirabilis and Staphylococcus aureus. The killing in vitro of E. coli and P. mirabilis, engulfed within an abscess, was significantly less than that of the same organisms when they were added to the in-vitro assay. In contrast, the killing of S. aureus was similar, whether engulfed in vivo or in vitro. However, S. aureus was less susceptible to phagocytosis and killing in vitro than P. mirabilis or E. coli, and the killing of S. aureus during in-vitro incubation of neutrophils that had engulfed the organism with in the abscess was similar to that of the gram-negative bacteria engulfed within the abscess.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional neutrophils from long-term murine bone marrow cell cultures

Murine bone marrow cell cultures that had been established for up to 26 weeks were harvested each week and found to provide functional neutrophils. Leukocytes harvested from the cultures were enriched for neutrophils using discontinuous Percoll density gradients. These cells mounted a chemiluminescence response to Proteus mirabilis in the presence of normal mouse serum (NMS). They killed several NMS-opsonised bacterial species, an activity that was blocked by a monoclonal antibody to the C3 receptor of mouse neutrophils. Cultured bone marrow neutrophils expressed both Fc and C3 receptors. C3 receptor expression could be augmented by exposure to the chemotactic peptide f-Met-Leu-Phe. We conclude that murine bone marrow cell cultures provide a useful source of functional neutrophils, and that their productivity can be sustained in long-term culture. As their receptor expression can be augmented from the resting state by exogenous stimuli, they represent a useful cell source in studies of neutrophil activation.

Differences in the phenotypes of cells mediating anti-tumour immunity at various stages of tumour progression in mice.

In Winn assays, T cells from donors immunized by tumour excision, or from mice with small tumours, mediate rejection of the metastasizing murine fibrosarcoma MC‐2. As the mean size of primary tumours in spleen donors increases, the strength of anti‐tumour activity declines, until it is frequently undetectable in spleen cells from mice with very large tumour burdens. Loss of splenic anti‐tumour activity is coincident with the appearance of cells capable of suppressing an otherwise protective anti‐tumour response in Winn assays. This paper defines the phenotypes of T cells mediating immunity against MC‐2. Eleven or more days after tumour inoculation the proportions of tumour‐bearer splenic leucocytes expressing Ly 1.2 (CD5), Ly 2.2 (CD8a) or L3T4 (CD4) surface antigens were significantly less than similar preparations from normal animals. Depletion of Ly 1.2+ or L3T4+ cells from spleen cells of donors with small tumours, or from donors immunized by tumour excision, diminished protection in the Winn assay. Depletion of Ly 2.2+ cells from these donors had no effect on immunity. In contrast, spleen cells taken from donors with large tumours lost all anti‐tumour activity if pretreated with any one of anti‐Ly 1.2 or anti‐Ly 2.2 or anti‐L3T4 antibodies in the presence of complement. These results suggest that cells bearing the Ly 2.2 marker may be important to weak immunity remaining in the spleens of mice with large tumours, but are not critical to strong immunity generated early in tumour growth, nor to that following tumour excision. That is, in addition to an Ly 1.2+, Ly 2.2−, L3T4+ spleen cell subset also seen early in the growth of the MC‐2 tumour, a cell population which expresses the Ly 2.2 marker and which is important to anti‐tumour immunity emerges late in tumour growth.

The effects of RU 41.740, a glycoprotein immunomodulating agent derived from Klebsiella pneumoniae, on intra-abdominal abscess formation in mice

The prophylactic and therapeutic efficacies of the immunomodulating agent RU 41.740 (a glycoprotein extract from Klebsiella pneumoniae) were studied in a murine model of intra-abdominal abscess formation with Bacteroides fragilis, Escherichia coli, and bran as an abscess-potentiating agent. Parenteral injection of RU 41.740, either before or after injection of an abscess-inducing mixture (AIM), was associated with significantly diminished incidence and size of abscesses. Abscess incidence and size were significantly decreased by oral administration of RU 41.740 after, but not before, AIM injection. Abscess formation and resolution are the results of complex interactions of host defence mechanisms with bacteria and potentiating agent, and RU 41.740 has been shown previously to activate both macrophage and neutrophil function. These results indicate that activation of non-specific defences may protect against abscess development in chronic sepsis.