Cytokine secretion from monocytes persists differentially after activator removal-One mechanism of long-term biological response to implants.

Biomedical implants significantly improve the quality of life in an ever-increasing number of patients. However, inflammation of tissues around implants remains a long-term, post-placement sequelae that may contribute to implant failure. Infection-mediated failure is partly a consequence of inappropriate host response and chronic inflammation, and is mediated primarily by the secretory products of monocytes and macrophages. Although the secretion of inflammatory mediators from activated monocytes is well characterized, the resolution of mediator levels post-activation is relatively unstudied. The current study defines the time course of cytokine secretion by activated human monocytes after the activator has been removed. THP1 human monocytes were activated by LPS, and cytokine secretion was monitored over time after LPS removal using enzyme-linked immunosorbent assays (TNFalpha or IL8) or a cytokine array. The release of cytokines was compared with conditions without LPS removal. As expected, secretion of nearly all cytokines was reduced when LPS was removed, but the amount of the reduction was highly cytokine-dependent. Furthermore, levels of cytokines were stable in medium alone but not in cell-culture, suggesting an active process to either degrade or internalize secreted cytokines. Our results are consistent with clinical experience that inflammation resolves rapidly after treatment to remove bacteria or inflamed tissue. However, the differential cytokine regulation indicates a sophisticated coordination of cytokine levels probably associated with management of the wound healing response after removal of the bacterial insult. This wound healing response is one critical component of the long-term success of biomedical implants.

Adherence of Plasmodium falciparum infected erythrocytes to CHO-745 cells and inhibition of binding by protein A in the presence of human serum.

Adhesion of erythrocytes infected with the malaria parasite Plasmodium falciparum to human host receptors is a process associated with severe malarial pathology. A number of in vitro cell lines are available as models for these adhesive processes, including Chinese hamster ovary (CHO) cells which express the placental adhesion receptor chondroitin-4-sulphate (CSA) on their surface. CHO-745 cells, a glycosaminoglycan-negative mutant CHO cell line lacking CSA and other reported P. falciparum adhesion receptors, are often used for recombinant expression of host receptors and for receptor binding studies. In this study we show that P. falciparum-infected erythrocytes can be easily selected for adhesion to an endogenous receptor on the surface of CHO-745 cells, bringing into question the validity of using these cells as a tool for P. falciparum adhesin expression studies. The adhesive interaction between CHO-745 cells and parasitized erythrocytes described here is not mediated by the known P. falciparum adhesion receptors CSA, CD36, or ICAM-1. However, we found that CHO-745-selected parasitized erythrocytes bind normal human IgM and that adhesion to CHO-745 cells is inhibited by protein A in the presence of serum, but not in its absence, indicating a non-specific inhibitory effect. Thus, protein A, which has been used as an inhibitor for a recently described interaction between infected erythrocytes and the placenta, may not be an appropriate in vitro inhibitor for understanding in vivo adhesive interactions.

Using starburst dendrimers as linker molecules to radiolabel antibodies.

Starburst dendrimers, spherical polymers constructed from methyl acrylate and ethylenediamine, were successfully used to covalently couple synthetic porphyrins to antibody molecules. The dendrimers, as linker molecules, have great potential for increasing the specific activity of radiolabeled antibodies for tumor therapy and diagnosis.

Immunoglobulin heavy chain haplotypes in caucasian New Zealanders.

In the course of studies on the genetic basis of autoimmune disease, immunoglobulin allotypes were measured in New Zealand people of caucasian origin. We report the observed frequencies of the various allotypes of the gamma heavy chains, together with the frequencies of the combinations observed to occur in individuals (phenotypes) and the nature and frequency of the combinations on individual chromosomes (haplotypes), as calculated by application of Kurczynski and Steinberg's computer programme MAXIM.

A solution to the genetic and environmental puzzles of insulin-dependent diabetes mellitus.

Studies of the segregation of heterozygous immunoglobulin allotypes in families with several cases of insulin-dependent diabetes mellitus (IDDM) show that germline heavy-chain V (variable region) genes are not major genetic determinants for IDDM, but data for IDDM and Graves' disease together suggest involvement of kappa light-chain V genes. Absence of IDDM at birth, the semi-random age of onset, and the 50% discordance of identical twins suggest that somatic mutation of germline V genes is involved in the development of the pathogenetic anti-beta-cell clones. The effect of histocompatibility and other alloantigens on the prevalence of IDDM is readily accounted for by the effect of the "holes" they induce, by natural tolerance, in the immune response repertoire; these alterations apparently affect the chance of emergence of anti-beta-cell clones by the somatic mutations and network of interclonal deletions that constantly change the fringes of the repertoire. Histocompatibility antigens can also influence repertoire development by changing the specificity of conjoint presentation of foreign antigens by macrophages. Antigenic stimulation by particular environmental microorganisms is probably essential to the repertoire development necessary for the occurrence of IDDM. Additionally, beta-cell damage by local infection may play a part by facilitating autoantigen presentation to the immune system.

On the nature of the genes influencing the prevalence of Graves' disease.

Burnet's theory that Graves' and other autoimmune diseases are caused by forbidden clones of immunocytes, reactive against host antigens and emerging in post-natal life due to somatic events (somatic mutations of V genes and inter-clonal deletions), remains the most comprehensive and likely concept of the pathogenesis. The MHC antigens, B8 and D/DR3, have a predisposing influence of X 2.5 and X 3.7 respectively, whilst male sex has a protective influence, divided by 6. Family studies testing for associated inheritance of Graves' disease and immunoglobulin allotypes (Gm and Km), by observation of the segregation of known heterozygous allotypes and also by Penrose's sibling pair method, have failed to show involvement of immunoglobulin genes. The H gene theory, prompted by studies on the inheritance of autoimmune diseases in the New Zealand mice, postulates that germline genes influencing the prevalence of Graves' and other autoimmune diseases code for major and minor histocompatibility or other alloantigens. By deleting complementary clones, alloantigens alter the immune response repertoire of each individual and this could alter the chance of emergence of a forbidden clone by the somatic mutations and the inter-clonal deletions envisaged by Burnet and Jerne. The H gene theory is superior to the linkage disequilibrium theory in that it accounts for all the known genetic features of Graves' disease, including the female sex preponderance, which is ascribed to the effect of clonal deletions imposed by the H-Y antigen.