A murine monoclonal antibody specific for calf intestinal alkaline phosphatase has been prepared and used in an unlabeled antibody bridge technique for labeling monoclonal antibodies. This procedure-the alkaline phosphatase monoclonal anti-alkaline phosphatase (APAAP) method-gives excellent immunocytochemical labeling of tissue sections and cell smears, comparable in clarity and intensity to that achieved with immunoperoxidase labeling. If the enzyme label is developed with a naphthol salt as a coupling agent and Fast Red or hexazotized new fuchsin as a capture agent, a vivid red reaction product is obtamed which is very easily detected by the human eye. For this reason the APAAP technique was found particularly suitable for labeling cell smears (for both cytoplasmic and surface-membrane antigens) and for detecting low num-APAAP 220 CORDELL ET AL APAAP STAINING OF MONOCLONAL ANTIBODIES

Chaperonins assist the folding of other proteins. Type II chaperonins, such as chaperonin containing TCP-1(CCT), are found in archaea and in the eukaryotic cytosol. They are hexadecameric or nonadecameric oligomers composed of one to eight different polypeptides. Whereas type I chaperonins like GroEL are promiscuous, assisting in the folding of many other proteins, only a small number of proteins, mainly actin and tubulin, have been described as natural substrates of CCT. This specificity may be related to the divergence of the eight CCT subunits. Here we have obtained a three-dimensional reconstruction of the complex between CCT and alpha-actin by cryo-electron microscopy and image processing. This shows that alpha-actin interacts with the apical domains of either of two CCT subunits. Immunolabelling of CCT-substrate complexes with antibodies against two specific CCT subunits showed that actin binds to CCT using two specific and distinct interactions: the small domain of actin binds to CCTdelta and the large domain to CCTbeta or CCTepsilon (both in position 1,4 with respect to delta). These results indicate that the binding of actin to CCT is both subunit-specific and geometry-dependent. Thus, the substrate recognition mechanism of eukaryotic CCT may differ from that of prokaryotic GroEL.

It is concluded that antibody JC70 is of value for studying benign and malignant human vascular disorders in routinely processed tissue.

The distribution of the pan-macrophage CD68 antigen, recognized by six different monoclonal antibodies, was examined in human blood, tissue, and cell lines using APAAP staining and Western blotting. All antibodies stained monocytes and macrophages, but labelling of neutrophils, basophils, and lymphocytes was seen with some of the reagents. In addition, the CD68 antibodies demonstrated a variety of staining patterns on some non-haemopoietic cells. The subtle differences between the reactions of the different antibodies suggested that the CD68 antigen may be heterogeneous, possibly due to differences in glycosylation. While CD68 antibodies are very useful markers of the macrophage/myeloid series, the presence of small amounts of the antigen on some lymphoid and non-haemopoietic cells means that care should be taken when using them for the diagnosis of tumours of unknown origin.

A number of linear and conformation-dependent neutralizing monoclonal antibodies (MAbs) have been mapped to the first and second variable (Vi and V2) domains of human immunodeficiency virus type 1 (HIV-1) gp120. The majority of these MAbs are as effective at neutralizing HIV-i infectivity as MAbs to the V3 domain and the CD4 binding site. The linear MAbs bind to amino acid residues 162 to 171, and changes at residues 183/184 (PI/SG) and 191/192/193 (YSVGSS) within the V2 domain abrogate the binding of the two conformation-dependent MAbs, 11/68b and CRA-4, respectively. Surprisingly, a change at residue 435 (Y/H or Y/S), in a region of gpl20 near the CD4 binding site (M.

On human B cells the antigen receptor complex is composed of the membrane form of the immunoglobulin molecule and the non-covalently associated Ig alpha/beta heterodimer. A small subpopulation of normal B cells and chronic lymphocytic leukemia B cells express (analogous to T cells) the transmembrane molecule CD5, a counterstructure of B cell-specific CD72. Numbers of CD5+ B cells are increased in several physiological and pathological conditions. Moreover, CD5+ B cells are being held responsible for the production of autoreactive antibodies and seem to have signaling characteristics distinct from conventional B cells. On T cells, CD5 associates with the T cell receptor CD3 complex and ligation of CD5 leads to the generation of co-stimulatory signals, that act on T cell activation. We here demonstrate that CD5 is associated with the B cell receptor (BCR) complex and serves as substrate for BCR-induced tyrosine kinase activity. Hence, CD5+ B cells have a unique potential to modulate BCR signals.

The tissue distribution of the human b b 3 -adrenoceptor studied using a monoclonal antibody: Direct evidence of the b b 3 -adrenoceptor in human adipose tissue, atrium and skeletal muscle 2,3 The human b 3 -adrenoceptor was later cloned by Emorine et al. 4 The pharmacology of the cloned b 3 -adrenoceptor agreed with the pharmacological data previously obtained in rodent adipose tissue, gut, and skeletal muscle in that the badrenoceptors in these tissues were insensitive to classical b-adrenoceptor antagonists such as propranolol.5 ± 8 Aryloxypropanolamine b 1 ab 2 adrenoceptor antagonists, exempli®ed by CGP12177, evoke a lipolytic response in rat adipose tissue through agonism at b 3 -adrenoceptors. 9 Similarly, selective b 3 -adrenoceptor agonists, such as BRL-37344, showed similar or greater potency than isoproterenol in stimulating lipolysis, but were much less potent than isoproterenol in stimulating responses mediated by b 1 -or b 2 -adrenoceptors. 10 The assessment of the pharmacological role of b 3 -adrenoceptors in human tissues has proved more controversial. For example, lipolysis in human white adipocytes induced by isoproterenol is sensitive to propranolol.11 Also, CGP12177-induced lipolytic responses have been demonstrated by some 12 ± 14 but not others. 9,15 It is now evident from comparisons of cloned human and rat b 3 -adrenoceptors that there are signi®cant species differences in pharmacology. 16 Attempts to detect b 3 -mRNA in human tissues using reverse-transcription PCR have also given conicting results. Krief et al 17 detected b 3 -adrenoceptor mRNA in several tissues, including gall bladder, adipose tissue and colon, while Thomas and Liggett 18 failed to detect a b 3 -adrenoceptor signal. Recently, RNAase protection assays, that do not rely on ampli®cation techniques, were used to identify b 3 -adrenoceptor mRNA in a variety of human tissues, including

Antibodies grouped together by the Third Workshop on Leucocyte Differentiation Antigens on the basis of pan-macrophage reactivity on tissue sections were analysed in immunoprecipitation experiments. Antibodies Y2/131, EBM11, Ki-M6 and Ki-M7 all precipitated antigens of Mr 110,000 which were shown to be identical by preclearing experiments. In addition a recently produced antibody, KP1, which identifies macrophages in paraffin-embedded tissue, was shown to recognize the same antigen. The antibodies were tested on murine cells transfected with two clones, which had been isolated by screening a cDNA library with antibodies Y1/82A and EBM11. Cells transfected with the longer cDNA clone, coding for a molecule of Mr 110,000, reacted with antibodies Y2/131, EBM11, Y1/82A and Ki-M6, whilst the shorter clone, encoding a molecule of Mr 70,000 gave the same result except that it did not induce expression of the Ki-M6 epitope. KP1 antibody did not recognize any transfectants, possibly because of differences in glycosylation by the transfected cell line compared with human tissue. Five of the six antibodies appear to recognize different epitopes (the sixth, Ki-M7, not having been evaluated in this way). It was concluded that these six antibodies react with a macrophage-associated antigen for which the gene has been cloned. This group of antibodies has recently been designated CD68 by the Fourth Workshop on Human Leucocyte Differentiation Antigens.