The 13 patients with AUTS2 syndrome with unique pathogenic deletions scattered around the AUTS2 locus confirm a phenotype-genotype correlation. Despite individual variations, AUTS2 syndrome emerges as a specific ID syndrome with microcephaly, feeding difficulties, dysmorphic features and a specific behavioural phenotype.

The association of Rickettsia prowazeki with L cells was examined by using a novel radioactive assay in which [a-32P]ATP-labeled rickettsiae were incubated with L-cell monolayers. Rickettsial association with the monolayer involved adherence and internalization steps that could be experimentally distinguished. Since R. prowazeki but not L cells possess an ATP-ADP obligate exchange transport system, addition of excess unlabeled ATP resulted in exchange of the labeled ATP from external, adherent rickettsiae but not from internalized rickettsiae. Rickettsial association was temperature dependent and was a linear function of both time and concentration. More than 90% of the biologically active rickettsiae associated with L cells was internalized. Rickettsial internalization required active participation of both rickettsiae and L cells; inactivation of either greatly reduced internalization. Rickettsial adherence to poisoned L cells was a saturable function of time and concentration. Adherence showed less temperature dependence than did internalization, but like rickettsial internalization, the extent of adherence was extremely low at 0°C. The rate and extent of adherence by inactivated and native rickettsiae to inactivated L cells were similar. Although inactive rickettsiae adhered to active and inactive L cells to a similar extent, inactive rickettsiae were internalized poorly by active L cells. These data form the basis for the hypothesis that R. prowazeki are internalized by the host cell through a process of "induced phagocytosis" and that inactivated rickettsiae adhere to the host cell differently from native rickettsiae, failing to trigger the endocytosis mechanism.

Rickettsia prowazekii, Madrid E strain, was assessed for its ability to enter endothelial cells derived from the veins of human umbilical cord in vitro. Rickettsial entry increased linearly with multiplicity of infection up to a multiplicity of 500; thereafter, additional rickettsiae adhered, but without a concomitant increase in the number of intracellular rickettsiae. Rickettsial entry required participation both of rickettsiae and endothelial cells; inactivation of rickettsiae with N-ethylmaleimide or Formalin, or of endothelial cells with cytochalasin B or D or NaF greatly reduced rickettsial entry. Because rickettsiae adhered to inactivated endothelial cells, adherence could be examined in the absence of entry. Rickettsial adherence was inhibited by poisons that inhibited rickettsial hemolysis. Calcium ionophore A23187, which did not inhibit endothelial pinocytosis, stimulated rickettsial adherence to endothelial cells, but inhibited rickettsial entry. These results indicated that typhus rickettsiae entered endothelial cells via induced phagocytosis, and that the signal for entry, which was dependent upon rickettsial energy, probably involved formation of a calcium gradient.

Bartonella bacilliformis was cultivated on a solid medium, and two bartonella colonial morphologies were differentiated and designated colony types Ti and T2. Although both Ti and T2 bartonellae adhered to human erythrocytes in vitro, approximately twice as many T2 bartonellae adhered as did Ti. Maximum adherence required bartonella energy, most likely proton motive force-dependent motility. Bartonellae did not penetrate or lyse erythrocytes in vitro. Bartonellae adhered poorly to a-or ,8-glucosidase-treated erythrocytes, but pronase or subtilisin treatment of erythrocytes stimulated adherence. This indicates that bartonellae probably adhere to an erythrocyte glycolipid moiety.