Claus Nielsen

THE ROLE OF COMPLEMENT RECEPTOR TYPE 1 (CR1, CD35) IN DETERMINING THE CELLULAR DISTRIBUTION OF OPSONIZED IMMUNE COMPLEXES BETWEEN WHOLE BLOOD CELLS : KINETIC ANALYSIS OF THE BUFFERING CAPACITY OF ERYTHROCYTES

Erythrocytes (E) express complement receptor, type 1 (CR1, CD35), by which they bind opsonized immune complexes (IC) in competition with leucocytes expressing higher numbers of CR1 as well as other complement‐ and Fc‐receptors. This may prevent inappropriate activation of phagocytic cells. We examined the distribution on whole blood cells of preformed tetanus toxoid (TT)/human anti‐TT IC, opsonized in situ in 80% autologous serum. Binding to E occurred rapidly and reflected the kinetics of C3‐fragment incorporation into the IC. Among eight donors, expressing 180–361 CR1 per E, >90% of the cell‐bound IC were associated with E from 1 to 5 min of incubation, decreasing to 12±13% after 40 min. Upon comparison of the IC‐binding to leucocytes in whole blood with that of isolated leucocytes we found that E, despite their extensive early complex uptake, only reduced the IC‐deposition on polymorphonuclear leucocytes (PMN) by 61±26% after 30 seconds of incubation and 47±14% after 5 min. During the subsequent 10 min, this buffering capacity of E was essentially abolished. E restricted the initial IC‐binding to B cells by 73±19%, but from 3 min of incubation the presence of E promoted, in a CR1‐dependent manner, a progressive uptake via CR2 by the B cells. CR1 was the dominant receptor in the early IC‐uptake by B cells as well as PMN and monocytes, since CR1‐blockade inhibited the initial IC‐uptake by these populations in a preparation of isolated leucocytes suspended in serum by ≥84% after 30 seconds of incubation. We conclude, that E exert a substantial buffering effect on the IC‐deposition on PMN, monocytes and B cells, while CR1 is the dominant receptor in the uptake by these cells. However, this effect is short‐lived and less than expected from the proportion of IC bound to E. Moreover, E are efficient processors of IC‐attached C3b/iC3b fragments to C3dg as indicated by a pronounced enhancement by E of IC‐uptake via CR2 on B cells. We propose that this mechanism may play a role in preventing phagocyte activation via CR3.

Diminished ability of erythrocytes from patients with systemic lupus erythematosus to limit opsonized immune complex deposition on leukocytes and activation of granulocytes

OBJECTIVEnTo compare the ability of normal erythrocytes and erythrocytes from systemic lupus erythematosus (SLE) patients to bind immune complexes (IC), thereby inhibiting IC deposition on polymorphonuclear leukocytes (PMN) and the consequent induction of a PMN respiratory burst (RB).nnnMETHODSnThe binding of fluorescein isothiocyanate-labeled IC in 75% autologous serum to whole blood cells or isolated leukocytes from 17 SLE patients and 10 controls was assessed by flow cytometry. Reactive oxygen metabolite (ROM) production by PMN was measured as the intracellular oxidation of dihydrorhodamine 123, on stimulation with unlabeled IC.nnnRESULTSnErythrocyte-mediated inhibition of IC uptake by PMN reached a mean +/- SD maximum of 68 +/- 18% in controls and 29 +/- 51% in SLE patients (P < 0.05) and, in the patients, correlated inversely with disease activity. In the presence of erythrocytes from various donors, IC binding to a standard preparation of PMN and their ROM production were inversely proportional to the number of type 1 complement receptors (CR1) per donor erythrocyte. Thus, the ROM production was higher in the presence of SLE patients erythrocytes (125 +/- 67 CR1/erythrocyte) than with erythrocytes from controls (235 +/- 118 CR1/erythrocyte).nnnCONCLUSIONnErythrocytes from SLE patients are defective in protecting their PMN against IC deposition and induction of the RB.

Synthesis of Novel 3′-C-(Hydroxymethyl)thymidines and Oligodeoxynucleotide Analogues Containing Compressed 3′-C-Hydroxymethyl-Linked Phosphodiester Backbones

Abstract Lombardo methylenation of the novel 2′-deoxy-3′-ketonucleosides 4 afforded 2′,3′-dideoxy-3′-C-methylene nucleosides 5, which were subjected to catalytic dihydroxylation reactions. In the case of 5′-deoxynucleoside 5a, a 1:1 mixture of 3′-C-hydroxymethyl diastereoisomers 6a and 7a was obtained, whereas the 5′-O-silylated nucleoside 5b afforded 3′-C-(hydroxymethyl)thymidine derivative 6b as the only product. Sharpless asymmetric dihydroxylation of 5a proceeded in low yield to give 6a and 7a as a 10:3 mixture. 5′-O-Silylated nucleoside 6b was converted into the phosphoramidite synthon 9, which was applied in automated syntheses of oligodeoxynucleotides containing novel compressed 3′-C-hydroxymethyl-linked phosphodiester backbones.

Synthesis of 1-substituted indole-3-carboxaldehyde related to acyclic nucleosides and their condensed pyrenyl derivatives

Indole-3-carboxaldehyde was N-alkylated to give the corresponding acyclic nucleosides 3a–h which were condensed with 1-pyrenamine and 1-acetylpyrene to give 5a,c,e–g and 7b–d,e,g, respectively. The Schiffs bases 5a and 5e with 2-hydroxyethyl and methylthiomethyl N-1 substituents were found moderately active against HIV-1.